For Arena, I plan to run the Shamans with a Healer friend. And the DK I'll be doing arenas solo with friends. I never liked the idea of healing the shamans with my Paladin in arenas, because I felt too immobile. I also don't care for PVPing with my Paladin, all in all I've found the DK to be a welcome solution to the few issues I've had with my Paladin, the Pali isn't going away though, not by any means. He's simply tanking for my mixed team now. All in all, the DK is fairly comparable to the Paladin in PVE. With a bit more damage output. And honestly, I think a bit more threat. Overall, I'm pleased enough to bench my geared pali in favor of using the ungeared newb DK.