I like to play at the Tier 2-3 level, to be honest. I typically powergame just a little with a Tier 2 (to the point of being 1.5 or 1), but hold back unless the party runs into trouble. I like playing the Deus Ex Machina without requiring the DM to be that if we run into trouble. It's worked well so far for the majority of my games, but I'll be honest, I've gotten some nasty looks from my fellow players (as well as my fair share of 'Why didn't you do that earlier?') when I do it - but they're happy enough to not be dead to overlook it.
Plus, I only have to haul out that combo every so often, because the rest of the players are playing stuff that can actually contribute without destroying parity. It makes for a nice balance point between the players, I find.
Tier 3-4 also does this, but there's less often a Player Ex Machina that can haul the party out of trouble and lead to a TPK - and TPKs disrupt the narrative, and I've always been more of a fan of participating in a story than owning in battle.
That's just my experience, anyways.
