I am leveling via instances because I am tired of questing and to learn the dungeons. My 1st 2 80 had zero time in any LK dungeon so the struggled, the DK is still behind the curve. Also healing is fun and not that hard as you get to know the classes.
Most DKs are sux Tanks before 80. I know because I am one, but I had one today; 20HP and not Def Capped, went down like a stone even with every heal on him. Pallys were usually the best, some of them healed the group more than I had to.