I know it sounds crazy now, but Iron Man had his own successful franchise, stars (and characters) didn't usually jump over to other films, and more importantly, Tony had been kicked out of the Avengers initiative by Fury. So yes, I was afraid he wasn't going to be a big part of it.
I'll be pleasantly surprised if Battfleck has a big role, but it does seem to me he's popping in to help with the narrative and maintain continuity from Barry's previous JL appearance.