Tested it the other night when I was bored. Theory that more int gives more power might be right, but not via the Acuity Buff. Buffing myself (on Usp) with my BBs Acuity buff does not increase the power pool. I gain 33 power a tick from a FoP with and without the buff. Only thing might be is that the FoP regens depending on your base power pool? Doubtful. Theory that more int raises damage? Nope, still the same cap with or without the buff, 609 on baseline DD both times. Reduces Variance on damage? Don't think so, cause I did roughly the same average damage over 80 casts on a lvl 50 hero with no resist buffs up on him, damage was 587.6 per cast with buff and 588.3 without, discounting the crits and resisted spells. So, what does it do? Only other thing is the resist rate... and I cba to test that.