The thing is, 4e really is a game of inches. Even though no one thing is wrong with a specific subpar character build the result can still be pretty ineffective sometimes. Not that the OP's character sounds like its ineffective, but you can't focus on ONE specific piece of advice in most cases which will just "fix" a character. It usually has to be a number of things taken together which are each fairly trivial by themselves.
In this case he has a couple of stats that could be dumped harder which is going to give him another point in a more useful stat. That's one little thing. He might also drop a point of DEX (I think) and still make his target prereqs. Little adjustments that may add up a bit, though they aren't going to suddenly turn him into a damage machine. The same goes for his weapon choice and feat selections. If he takes proficiency in a superior +3 bonus weapon, that will add a bit. Throw in a good damaging at-will (Righteous Brand is the only sane choice) and he can go from a +6 to-hit to a +8 to-hit which is a straight up 20% DPR increase right there, and with doing say 1d10 vs d8 damage all of a sudden it means he can dish out a good bit more hurt. He's still not going to be a DPR king, just he'll do enough to make it probably worth using RB instead of Astral Seal constantly.
I do know what you mean though about the pacifist powers being almost too good to turn down. One of the problems is its pretty much always better to debuff the enemy's defenses vs buffing one of your own guys to-hit. Someone said something about equality, but there are ALWAYS ways to gang up on those sorts of debuffs with a smart party. If I give player X a +2 to-hit on his next swing, that's it, it has one use. If I can put a -2 on the enemy's AC for any duration at all other players can use readied actions etc to pile onto it.
In any case, the character seems to be fairly effective. Honestly if it was me I'd play to your strengths and not worry about damage too much.