Ah, now all the interesting combos come up. Good!
(edit) Thanks for the feedback. Also, first set of feats is up.
Good point.
Upon further investigation, Myrmidarch is worse than I thought, because it can't attach a touch attack to an arrow; you can only attach a ranged spell to an arrow, which increases its range at the cost of accuracy (since it now targets regular AC instead of touch AC). That's not a great deal; if you want more range, either use Reach Spell or spells that have medium range to begin with. And oddly enough, Spell Combat requires a melee weapon, and Myrmidarch doesn't change that (nor does Card Caster and nor does Throwing Magus).
On the other hand, the Card Caster can actually attach any touch attack to a thrown weapon to increase its range to at least 20'; even though the rest of the archetype is not so great, this ability is good and he doesn't give up a lot for it (and can still take Hexblade, Kensai, or Staff Magus if so inclined). The only issue here is that a javelin or chakram is still a better weapon than playing cards. Ok, I'll give this some more room for discussion and then adjust the ratings accordingly.
Could you explain how you would use this in practice?
The way I see it, a warpriest can indeed benefit from recharging his ki with Irori's channeling, but he doesn't need a Magus arcana to do so. On the other hand, a Magus could dip one level into cleric and two into ninja to gain channel and ki, and can then recover about two pool points per day... or he could simply take three more levels in Magus (which gives +1 pool) and the Extra Pool feat for +2 more. So it seems to me that he doesn't really benefit from this trick.
Could you explain further how this combo works?
GTWF requires level 15. At that point, you could spend two feats/arcana on precise strike have an attack routine of +9/+9 (spellstrike)/+9 (haste)/+4/-1 for 1d6+15 (precise strike)+7 (dex)+5 (magic weapon), or 30.5 average damage. This could be boosted further by taking e.g. Bladebound or Kensai, and you can do it all day; you also have the option of using spellstrike for an actual damage spell.
Or you could spend four feats on TWF/ITWF/GTWF/Piranha Strike and have an attack routine of +6/+6 (haste)/+6/+1/+1/-4/-4 for 1d6+18 on your primary (+7 dex, +5 magic, +6 piranha for 21.5 average), 1d4+7 on your secondary (+4 magic, only +3 from piranha, for an average 9.5). This doesn't strike me as a good deal; even in the best-case scenario (if all your attacks connect, which really isn't likely with the penalties from piranha), you're looking at 114.5 average damage vs 152.5 for the regular Magus.
Two of the most common defensive measures, a Ring of Protection and the Protection From Evil spell line, both already give a deflection bonus.Spellblade Parry is worthy of note because it boosts your touch AC and CMD as well. My main issues with it are that it won't stack with other deflection bonuses (so if you get deflection elsewhere it's useless) and that it doesn't apply to ranged attacks/rays for no good reason.