new units spoiler section uses her awakened image. most units get a new art upon awakening, except a few such as bashira.
frankly speaking I'll probably try to mincost her too, but I can't spend too much SCs on her so I can only hope for the best =/ but aside from that, there are 3 good cc fodder farming maps. and gustav is pretty crappy, just keep him around as cc fodder. probably a good replacement for rosalie if you still have her remaining from previous events.
and lafate, I think you should add to your comments that it's basically mage-healer-tank combo for this event. high def units make archers pretty useless, so carpet bombing strategy's probably the best (and how I wish there was another ranged spot at the choke point to place a 2nd mage, would make things so much easier.)
also, doesn't rikka's skill increase her attack speed during skill? or did I misread her skill?