IMO you should never see +/- stat mod to attacks or defenses.
This. Most of my biggest concerns as powers go involve this guideline being violated. Platinum Scales, Psion Level 1 Powers, etc.
Or rather - if you see such big bonuses, they should be limited. A daily effect might give you such a bonus for a single round, not an encounter. An Encounter Power might give you such a bonus for a single attack, not an entire round.
I'd love to see them fix some of these mistakes, without me needing to come up with errata for them on my own.