Multiclassing...

[Vhaidara]

You are wildly, and I mean wildly, undervaluing how good a lot of multiclass feats are. I've got about 20 active 4e characters, and nearly all of them are multiclass one way or another, as early as level 5 in a lot of cases (which is when my group starts characters). To go down some of them
Paladin|Warlock/Fighter: uses multiclass to qualify for my Avernian Knight Paragon Path, which has a fantastic set of features and a great E11
Invoker|Cleric/Bard: picks up ritual casting via bardic ritualist and with Walk Among the Fey + Gloves of Dimensional Repulsion all of my giant bursts teleport 3 on hit
Psion|Swordmage/Fighter: Access to Polearm Momentum means that I can daze and prone enemies all over the place with Psychic Anomaly
Bard|Warlock/Sorcerer: opped up for a super high Arcana, Sorcerous Visions lets me use that skill for Perception and Insight
Rogue/Warlock: Hidden Lore gives me access to more options to become invisible, and Arcane MC means I can get a disembodied hand. You mentioned Quickdraw earlier, how do you like the sound of unlimited drawing and stowing as a free action? And in Epic she becomes a dragon, because why not?
Warlock|Wizard/Swordmage: Let's use a Weapon of Summer and add fire typing to everything so I get +2 to hit (Infernal Prince theme and Hellfire Blood feat) as well as a burst expansion at 16. I could take Arcane Implement Proficiency, but this comes with the added bonus of a skill training and daily +1 to AC end of encounter
Vampire|Warlord/Invoker: Staff is a weapon and an implement, so I can get a Radiant Staff to turn on my Morninglord fallen angel

All of these builds have their MC at their core, and that holds true for a lot of my builds. I've even got an Artificer|Battlemind who took the Traveler's Harlequin Paragon path and intends to, by 30, have taken 7 Multiclass feats, and a Runepriest|Druid who is taking every warlord multiclass feat (7 of them, plus Novice Power)

And generically, Resourceful Leader, Bravura Leader, Shadow Initiate, Battle Awareness, Binding Initiate, and Student of Divine Runes are probably among the best feats in the game, even if they didn't give you access to the associated class' support options (shadow initiate and student of divine runes practically don't have support).

As has been mentioned, the power swap feats are less popular because they are less pure plus and more of a trade, but also because you can have a multiclass that is not based on your primary or your secondary. My Wis/Con Cleric|Invoker won't get much mileage from powerswapping bard attacks that rely on Charisma to hit, for example. Novice power is the most popular because it provides the most consistent benefit: an encounter attack power. Combined with most classes having at least one level of meh encounter attacks in heroic, it's usually pretty easy to find something you want to swap out.

[ARTHAN]

You are wildly, and I mean wildly, undervaluing how good a lot of multiclass feats are. I've got about 20 active 4e characters, and nearly all of them are multiclass one way or another, as early as level 5 in a lot of cases (which is when my group starts characters). To go down some of them
Paladin|Warlock/Fighter: uses multiclass to qualify for my Avernian Knight Paragon Path, which has a fantastic set of features and a great E11
Invoker|Cleric/Bard: picks up ritual casting via bardic ritualist and with Walk Among the Fey + Gloves of Dimensional Repulsion all of my giant bursts teleport 3 on hit
Psion|Swordmage/Fighter: Access to Polearm Momentum means that I can daze and prone enemies all over the place with Psychic Anomaly
Bard|Warlock/Sorcerer: opped up for a super high Arcana, Sorcerous Visions lets me use that skill for Perception and Insight
Rogue/Warlock: Hidden Lore gives me access to more options to become invisible, and Arcane MC means I can get a disembodied hand. You mentioned Quickdraw earlier, how do you like the sound of unlimited drawing and stowing as a free action? And in Epic she becomes a dragon, because why not?
Warlock|Wizard/Swordmage: Let's use a Weapon of Summer and add fire typing to everything so I get +2 to hit (Infernal Prince theme and Hellfire Blood feat) as well as a burst expansion at 16. I could take Arcane Implement Proficiency, but this comes with the added bonus of a skill training and daily +1 to AC end of encounter
Vampire|Warlord/Invoker: Staff is a weapon and an implement, so I can get a Radiant Staff to turn on my Morninglord fallen angel

All of these builds have their MC at their core, and that holds true for a lot of my builds. I've even got an Artificer|Battlemind who took the Traveler's Harlequin Paragon path and intends to, by 30, have taken 7 Multiclass feats, and a Runepriest|Druid who is taking every warlord multiclass feat (7 of them, plus Novice Power)

And generically, Resourceful Leader, Bravura Leader, Shadow Initiate, Battle Awareness, Binding Initiate, and Student of Divine Runes are probably among the best feats in the game, even if they didn't give you access to the associated class' support options (shadow initiate and student of divine runes practically don't have support).

As has been mentioned, the power swap feats are less popular because they are less pure plus and more of a trade, but also because you can have a multiclass that is not based on your primary or your secondary. My Wis/Con Cleric|Invoker won't get much mileage from powerswapping bard attacks that rely on Charisma to hit, for example. Novice power is the most popular because it provides the most consistent benefit: an encounter attack power. Combined with most classes having at least one level of meh encounter attacks in heroic, it's usually pretty easy to find something you want to swap out.

You forget two things and these two things are the reason you find that I wildly undervalue the MC feats.

1st: I do not consider taking just a single MC feat as a multiclass and I strongly believe that it should not be considered MC a "multiclass" without a single power-swap feat in its build.
2nd: I find Essentials and previous 4th edition material not very compatible to each other, so I wouldn't accept a MC between the two (in other words, I only accept previous 4e material MC or Essential material MC but not a mixture of the two).

[Vhaidara]

And yet all of these builds are reliant on their MC, and in many case on taking another feat or paragon path that would not be available without their MC. AND beyond that, half of the builds I listed do power swap, though generally towards the end of paragon because feats are precious.

As far as not including essentials...okay? I fail to see any kind of relevance here, since only one of these (the vampire|warlord) involves using an essentials class, and vampire can be changed out pretty easily for any Charisma class with a melee basic attack (warlock, for example). Most of these are a combination of Core classes, or PHB1-3 classes at most

[ARTHAN]

And yet all of these builds are reliant on their MC, and in many case on taking another feat or paragon path that would not be available without their MC. AND beyond that, half of the builds I listed do power swap, though generally towards the end of paragon because feats are precious.

As far as not including essentials...okay? I fail to see any kind of relevance here, since only one of these (the vampire|warlord) involves using an essentials class, and vampire can be changed out pretty easily for any Charisma class with a melee basic attack (warlock, for example). Most of these are a combination of Core classes, or PHB1-3 classes at most

I know that MC feats are needed in order to MC, I just do not find the MC complete just with them.

Like you said, feats are precious. And that's I've said it many times and I will say it again, the game should had all feats granting feat bonuses instead of untyped bonuses to prevent min-maxing to a great extent.

It's nice you used power-swapping examples and I really thank you for that because that is what I was mostly searching for.

Finally, yeah, the vamp-lord was the Essentials I was mostly talking about and it would be interesting to see it as a warlock-warlord combo instead.

[Vhaidara]

I don't know what you mean about making all feats grant feat bonuses. The best feats in the game, imo, don't give any kind of direct bonus, especially the ones I listed. They give qualitative changes, not quantitative ones. I'm an outlier in that I don't even tend to take damage feats on my strikers, I'm more likely to pick up ritual casting (ideally via bard MC, since bard has some really fun feats and unique rituals).

Generally speaking, if I want powers from another class, I'm more inclined to hybrid. I had a Rogue/Paladin I had fully built out who was swapping for 3 powers. I was talking to a friend, and she asked "why not just hybrid?" And when I looked at it, yeah, by going hybrid, I gained 3 feats (would have been 4, but I did need to take Hybrid Talent to pick up a class feature I needed and lost). So by going hybrid, I got back 3 feats and my MC, which in turn allowed me to take artificer for a daily heal, arcane feat access, staff proficiency, arcana training, and a side of thematic batmanning.

Likewise, I had a warlord/Fighter who was planning to power swap for Hydra Charge, and after playing her for a couple levels, I realized that she would lose very little by hybriding for the power and getting her fighter powers that way.

Meanwhile, on the side of not doing hybrids, I had a Monk/Rogue who power swapped for Low Slash so that she could use a Blurred Strikes Ki Focus to get 2 flurries off of Blistering Flourish>Low Slash. If she was hybrid, she couldn't have flurried on non-monk powers.

Hybrid and Multiclass are potent compliments to each other. They both bring something to the table, and they can be combined.

[MwaO]

Let me see...
Blackguard|Invoker MC Bard for access to Bard of All Trades, Arcane Familiar, Battle Song Expertise
Warlock MC Wizard for Novice Power(Dark Gathering), Enlarge Spell(2 Wizard wands, Dark Gathering, and Freezing Burst from Arcane Initiate
Warden|Sorcerer MC Wizard for Consuming the Weak, ongoing 5 fire damage any time I hit a target I'm giving vulnerability fire. Which is basically always.
Fighter MC Net Training, Shadow Initate, Binding Initiate, Arcane Familiar with Traveler's Harlequin
Bard|Invoker Blade Initiate to be able to use a blade as an implement and will later get Borrowed Confidence at 16th via power swap.
Monk MC Bard for access to Arcane Familiar, Walk Among the Fey, Religion skill(entry into Paragon Path)
Fighter|Vampire Resourceful Leader, Bravura Leader. At 11th gets Novice Power, 14th gets Adept Power for a daily
Seeker MC Invoker for Hand of Radiance+Novice Power for Thunder of Judgment
Artificer|Druid with Monastic Disciple for access to Healing Fist, MC Wizard with Traveler's Harlequin so as to pick up daily Wizard summons

Oh, and a Warden|Wizard without an MC feat planned out before Paragon.

That's all my current PCs.

[masteraleph]

Let me see...

Oh, and a Warden|Wizard without an MC feat planned out before Paragon.

You know this is contractually a violation of your build traditions and you're not allowed to play this, right?

[MwaO]

You know this is contractually a violation of your build traditions and you're not allowed to play this, right?

I'm part Wizard with picked up feats! I'll be lucky to have free feats by 18th!

[LibraryOgre]

I had a bard for whom EVERY feat was a multiclass feat. It was nuts. But it was hella fun.

Perhaps my biggest annoyance was that most of the Arcane classes, when multiclassed into, also gave proficiency in Arcane. Which was fine... unless you already had Arcane. Which you probably did. Because you were an Arcane Class. So being a Wizard with a touch of Sorcerer was less idea than a Wizard with a touch of Cleric, because Cleric would give you a new skill, Sorcerer would not.

I liked the more limited version of multiclassing feats presented, though. It avoided the synergy problems that 3e and 5e have both run into... "I combine X and Y and can now do OMEGA!"