The only reason it's less useful in a raid is because you have more Atonements to juggle and thus less opportunities to cast Smite, generally speaking. But I still try to follow every Penance immediately with a Smite, it still procs quite often and it definitely improves HPS in a raid at key moments in a fight with the right setup. There are plenty of predictable raid damage mechanics where you hand out Atonements beforehand then become a DPS turret for 10 seconds, and a few Cord procs in there can mean a big difference in HPS, especially if PI, Innervate, or Lust are up.
I still don't think canceling a cast for Penance is worth the brain power or chance of lowering output due to reaction time and latency. Worrying about Atonements and fight mechanics is plenty to be concerned with until I've got Mythic Xavius on farm, and even then I have doubts that canceling is a practical improvement in output. I also don't think it's a good idea to have Penance in a cast-cancel macro in general as it makes it more difficult to optimally cast it at the end of another spell's cast bar, especially if your internet connection is inconsistent as mine is.
Last edited by Xepperoni; 2016-10-14 at 06:17 PM.
Yeah, it's less useful in raids because:
-You're casting less Smites
-You've got other things to pay attention to, thus you can't really give a whole lot of attention to sharply watching your Penance CD for resets
I really only make the best use of the belt proc in content where healing/focus doesn't really matter, such as questing and random heroics.