Having played a Rogue, Hunter, and a DK to 80 (in that order), I definitely have to say that the DK is hands-down the best solo class. Pick a blood spec that has some avoidance and mitigation, as well as increased self-healing, and there is no downtime to heal AND no loss of dps while you sit in Aspect of the Viper to regain mana.

There were only four or five group elites that I asked a priest friend to help me with from 55 to 80; the rest were easily soloable at the level you're supposed to kill them.

The one major problem with Hunter is when moving from soloing to endgame for the first time, you have to completely relearn your class. Things you can get away with when mucking about while solo will get your party wiped in a raid. While that is true for most classes, it seemed to me as something hunters especially had an issue with.

I've gotta agree with M on the DK comment. When I leveled my 80 DK, I made the choice that I would never group for any quest, but still must complete every group quest. I have now finished Northrend Loremaster and all the group quests, every single one of them solo. Blood-tanking spec is truly overpowered. The only hard one was fighting Aurugal in Grizzly Hills becuase he would MC me, attack my bloodworms, then bug out and reset the fight. For this spec, I had to use my secondary DPS spec (unholy) without using my pet.

If you haven't played a hunter past lvl 11, you pretty much haven't played a hunter at all. You can't even get a pet until lvl 10, so you spend most of your time in melee range, which isn't what a hunter is about at all. And pet taking the most damage? Ludicrous, or at least it was when i lvled my hunter, since last i checked you're constantly pulling agro off the pet. i still have this problem with my bear, i thought thunderstomp supposedly enable a pet to tank a party (i've read impressive things to that effect), yet even with misdirect i pull agro off my pet with one shot. i do agree that playing a hunter is pretty complicated once you reach a certain level.