I think you're right that "combos" will arise. My complaint wasn't the lack of such tactics, but rather that meta-game constraints were needed at all.Maybe I am a bit to optimistic, but I think D&D 4 has both.
The 4E dailies are unique powers that are "reliable" to pull off (within the constraints of rolling d20s and so on).
But using all those at-will, encounter and daily powers together does create "meta-powers" - tactics and strategies that will usually prove effective (provided a given set of constraints, like "a lot of enemies are minions" or "there is a choke point" or "we're surrounded"). The trick is finding them, because they are not neatly labeled (yet)...
I'd like to see once-per-encounter exploits only be useful or possible roughly once per encounter, because conditions in the game actually aren't right, not useful or possible most of the time, but limited purely by the rule, which has no in-game rationale.