Just curious which changes did the OP try and how is it working so far? ...
I also agree that another valid point is what he is trying keep up with.
My PC has purchased a Belt of Giant Strength +2 (all he could currently afford). I just played him at a con over the weekend and it seemed to work out well; I know it's only a +1 for attack and damage, but sometimes that matters. :)
Having survived that scenario, I'll be leveling him up to 9th shortly. I plan to take the Improved Critical feat for his scimitar, and I'm excited to see how that works out. In addition to the multiplied damage, he also has the Flame of the Dawnflower trait, which adds 2 points of damage on crits.
I've been torn about the 2-handed attack strategy because my PC has invested in a +2 shield and I'm not keen on him selling it off ... Then I realized that he can just keep it slung over his shoulder and use it when he needs it. Duh. So I'll be trying out the 2-handed attack next time I play him, hopefully next month.
Still kicking around the feat retraining ideas. I might have him retrain Channel Smite for one of the feats others have suggested.
As for my points of comparison: In the past I've played with players whose PCs (like archers, or fighter-types with nasty, big, pointy melee weapons) seem to average in the 20's for their damage per attack, while my PC seems to average in the low teens, if that. I guess it's a bit embarrassing for me, sometimes, and not quite what I want my PC to be like (a fearsome warrior of good, a force to be reckoned with).
So that's where I'm at right now. Thanks for asking!