What can you do with Greensting Slayer Magus?

[Dusk Eclipse]

Pretty much what the tittle says, I just found out this archetype (http://www.d20pfsrd.com/classes/base-classes/magus/archetypes/paizo---magus-archetypes/greensting-slayer) and I was wondering how it affects the magus' overal power level. I personally don't think that loosing enhancing the blade with the Arcane pool is a big deal, since at higher levels you will probably have a "permanently" enchanted weapon (or you could have taken the Bladebound Archetype too which gives your blackblade a natural enhancement bonus).

While 5d6 at level 17 isn't really much, the extra damage is cool and you don't really loose much, at least in my opinion) and you can do two attacks from level 2 onwards via spellstrike+cantrip delivery; Hexcrafter (http://www.d20pfsrd.com/classes/base-classes/magus/archetypes/paizo---magus-archetypes/hexcrafter) may be needed so you can use the Brand (http://www.d20pfsrd.com/magic/all-spells/b/brand) orison cantrip

Having said that I'm not really sure if it is legal to combine all those 3 archetypes consider all of them have (x) in the column for the first Arcana (level 3), but neither of them really exchange the Arcana at all (with the exception of the Bladebound). Both Hexcrafter and Greensting simply add options to the choice of Arcana you can select.

Finally, given the name of the archetype I'm guessing the Greensting slayer might be some kind of organization or similar, is that the case?

[Bhaakon]

Magi get greater magic weapon, so I agree that trading off the weapon enhancement ability isn't necessarily a deal-breaker if the return is worthwhile, but one chance at a half-power sneak attack per swift action is not a worthwhile trade. Over the course of a battle, a vanilla magus would pile up more damage out of the surplus weapon enhancements working on every attack than a couple chances at a sneak attack per combat.

That being said, evasion/improved evasion is more useful than med/hvy armor proficiency for a dex-based magus, so it's not a total bust.

The fluff of the archetype ties it to a half-elven fighting academy in Kyonin, but there are no rules explicitly limiting it to half-elves or students of the academy.

[Dusk Eclipse]

Well it seems that at low levels it might be worthwhile, I mean 3d6 with minimum investment at level 1 is deadly, at level two you can throw two attacks each dealing 2d6 damage which isn't too shabby.

[Kurald Galain]

The main problem with this archetype is how many arcane pool points you have. The answer is "not a lot"; a low level magus can be expected to have three to five points per day. And remember that several of your magus arcana also run off this same pool.

So the archetype is basically "four times per day, you deal +3.5 damage with a single attack and this ability is wasted if the attack misses".

And that's a pretty bad deal.

[Dusk Eclipse]

.... how the hell did I miss that? Nevermind the archetype indeed sucks.

[StreamOfTheSky]

Even if the sneak attack lasted for a minute like the enhancements do, this archetype sucks. The enhancements are better and stack with whatever is already on there, so having GMW is irrelevant. The pool is adding a lot of potentially awesome specials to your weapon on the spot, especially with later arcana. Keen, Bane (after you know what type the foe is), Holy, ghost touch, etc...

And I'm not sure if you could use it with bladebound...both modify arcane pool.

[Muggins]

Multiclass into Ninja for two or three levels, then pick up the Ki Arcana arcana?

Although, admittedly, that functions better when the Magus half has that fancy new Eldritch Scion archetype.

[Shinken]

.... how the hell did I miss that? Nevermind the archetype indeed sucks.

Yeah, the best thing about it is evasion. That's saying something...
Really wish it worked well, though. Sneak attack + mobility + spells is something that rarely works well together, it would be fine to have it all in one neat package.
EDIT: About the fluff, it apparently originates in Erages. I have no idea what that means, though.

[Dusk Eclipse]

I think that simply giving the archetype a delayed sneak attack progression in exchange for the ability to enhance weapon might would have been perfect, or perhaps a "new" mechanic in the vein of ambush feats. Spend 1 point of the arcane pool as a swift/free/immediate to blind the enemy you hit with a sneak attack, spend 2 points to make them make a save or be staggered.