Clarifying just a little bit more on Yotsuyu (then I'll get off the topic for good because I think I've covered all the bases):
While I do think her actions in the end had positive consequences, her motivation remained fixated on vengeance - just directed at the people who deserved it instead of Domans in general. "Tsuyu" had definitely become a part of her, perhaps more than she was willing to admit to herself - she clearly doesn't want to go back to being the Witch of Doma, but knows that Asahi will never let her have the peaceful life Tsuyu might. Her actions then could be seen both as repaying Gosetsu for his kindness and as a giant "screw you" to Asahi - while she doesn't care much for Doma she still cares for Gosetsu and wants to spare him pain, while Asahi not only died by her hand but also with the knowledge that his carefully crafted plan had fallen to pieces. That Doma was spared another war and Garlemald granted a chance to expose the corruption growing within it were just positive byproducts.
The theatricality she employs before summoning, as well as the need for the add phase at all (and especially the Gosetsu phantom) all strongly suggest that she's trying to convince herself as much as anyone else that she's Yotsuyu the Witch of Doma, though. No matter what she tells herself or anyone else, that simply isn't true - the Witch of Doma died with the collapse of Doma Castle.
... that's what I'd like to believe, at any rate.
Anyway, enough of that depressing crap!
Shadowhunter:
I'd wager the main reason he's carrying around his old mask fragment (if it is indeed Gaius) is as a reminder of what trusting an Ascian cost him. At this point he's lost everything but his weapon, a good majority of it from trusting Lahabrea. He failed to conquer Eorzea three times - once before Legacy, once during, and during ARR - at this point he's likely a disgrace in Garlemald. Trusting Lahabrea's word with the Ultima Weapon, he went rogue and tried to conquer Eorzea only to be rebuffed by the Warrior of Light, marking him as a deserter punishable by death in his homeland. The Ultima Weapon itself proved far more destructive than he desired or intended, which led to his supposed death back in the Praetorium and probably burned / scarred him (notice the bandages on his free arm).
Gaius, at this point, would have little left but vengeance on the Ascians - carrying a reminder of his past life, and how they cost him that life, would be a very good reason. I think.
I doubt he chose this moment to reveal himself - he just helped some Garlean soldiers that had been shot down because, disgraced and exiled as he may be, he probably still loves his homeland. Alphinaud just happened to be on the craft. Coincidences do happen!
Four Lords
I haven't finished it quite yet (my iLvs are a bit too low for the instanced fight, or perhaps I just suck) but...
SON GOKU!!!
Ivalice
Haven't finished the raid, but thus far I'm still not engaged. I'll get to it over the long weekend.
Having to spend a modest amount of time fetching vintage wine for Yasumi Matsuno's avatar character for no real reason did not motivate me, though.