Maybe it's just been too long, but I actually cannot remember teaming up with a pain dom that was higher than early 30s after Going Rogue came out and we could have Empaths villain side. Like, even in raids. Maybe I am wrong, but it just isnt coming to mind, so I've been writing off the powerset for a long time, maybe I should look at it again on Mids.
I played an Empath defender designed to heal and heal well, and I loved it. I never played Pain Dom high enough to really comment on that side, but I can say that I had a purpled out Empath with focus on +healing and +recharge, and I could keep a raid healed when everyone was in range and have a blast doing it. People never complained about my buffs, and I even remember room being made for me on a couple Trials.
I think this may be true for some, but not all of these battle of the powersets, but it really comes down to if the player knows the set, knows what they are doing. Put one of the guys that I was almost always teamed up with in CoH on my healer designed to heal stupid amounts and he would still let team wipes happen, put him on a set he was comfortable with and he was fantastic.
Edit: Loading up Mids, I would say the biggest difference is that Defenders cant get Pain Dom, so PD only exists as a secondary set. For anyone wanting to play a dedicated healer this is a pretty big difference, Empathy on a secondary is considerably weaker than Empathy as a primary. I'm going to play with some builds and see what I can find as far as stats as secondary sets though, how well it would serve my playstyle on healers.