I think the best thing is, if you're elemental like me; wait until you have them to about 1/4 health. Most pallies won't try to use a bubble or lay on hands until just after this point. Than, hit elemental mastery, chain lightning, and an earthshock or frostshock. If he's not dead by now there's a very good chance he'l bubble/ LoH on you, at which point you're kinda screwed into doing it the old fasioned way, which really sucks unless you're doing awesome melee damage, because you're now likely out/low on mana. But basically, kite him around until 1/4 health than tear into him fast enough that he can't respond. It's always worked for me, the only time a ret pally can beat me is when his bubble AND lay on hands CD is up, AND he uses them way too much. (Bubble at half health? what the hell?)