Warning! random thoughts ahead:
Hmm I'm not sure about power attack. So if your weapon does a d12 it will add a d12 but a second attack would add a d12 +str and other bonuses but be at -5. If I'm not mistaken a d12 is as big as it gets to right? nothing like enlarge or monkey grip or anything like that would ever increase the die size it would most likely just give you a flat damage bonus. However I guess it does count as one action instead of 2 so maybe if you are doing other things then attacking and making just one attack its gonna be a solid option. Would have to go over the math that we don't have yet to really figure it out also maybe their are more feats to improve it?