I used to go all surge before switching back into alacrity. I have sorc healer and i used to stack surge just for a little extra on those heals. Then i started breaking down all of my ops runs in parses. I would heal around 1900 heals per second in full surge so way over the cap. Then i said i will try it with getting my surge down to around 300 and then the rest alacrity. My parses after that were almost always 2100 hps or more. So in the long run of fights it seems that that 0.1 or more off a cast is more effective.