Yeah, when I play mages, if I don't have removal, I always get messed up by Enrage minions. I like how it works though, most class hero powers interact with their cards pretty well. Mages, Warriors, Hunter, and Shaman and Druid to a lesser extent, really don't.
Don't take this as me saying they're bad / a problem. I'm just saying there is low class card synergy compared to other classes. They only have one or two cards that work with their hero power directly. As an example, Warriors only have Shield Slam, witch is the only card that directly uses armor, but armor is really good. Same with Shaman, they only have what, Totemic Might? (You can argue Blood Lust of course) That being said each totem is pretty good for what it does.
So it's cool that Mages can find some extra work with Enrage cards, because I can't think of a card that directly works with Fire Blast that's a class card.