Probably Phoenix there. She's a lot better in a game that has higher meter gain. She was also slightly nerfed directly between the two games too.
Maybe still Zero though I'm unsure how much of his power was from buffs.
Lots. Without the buster cancel he can't apply lightning loops and is less safe. Still great, just not super dominant.
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Twostuck, Homestuck RPG: http://www.gamefaqs.com/boards/8-gamefaqs-contests/62168402