True, but if the players don't report damage, then you wouldn't touch the monster's HP totals either.
Ultimately it might just depend on the party. The question of power choice would be easily addressed by knowing what the players can do. If no one has a daily that does more damage than an encounter, frex.
What about powers that specifically do more damage instead of applying effects?
What about powers that have powerful effects but specifically do lower damage (just stat modifier, or fixed damage).
What about ongoing damage?
What about auto damage that are not "hits" (zones, divine challenge etc)
What about feats and powers that give bonus damage for a period of time (Blessed weapon etc.)?
What about healing?