1. buffed dodge/parry stats: no shield means 20-30% avoidance lost and since DK's will likely not get huge stam pools or armor like druids they will need talents to maximize this.
2. Their tanking tree might contain a huge buff to their stam ala the paladin 26% stamina bonus with kings up. This would still have to be coupled with some sort of heightened parry/dodge build.
3. their tanking summons will somehow benefit their armor/ defensive stats like a bone shield of sorts.
4. Their tanking tree will NOT be their dps tree, for obvious reasons.
The reason i don't think they will have little off-tank summons is because that set up is not conducive to several aspects of the game. The pets wouldn't scale properly, if they did they would be a ridiculous threat in pvp, the only way I think their pets will be implemented will be as utility to build theat (exploding skeleton) or avoid the occasional attack (afformentioned bone shield, not in the held in off hand sense but in a wall of skelies eat an attack sense, like a shield block w/o the shield).
That being said DK tank will require tanking gear and probably warrior like skill (lets face it druid and pali tanks are easier to play and the DK ability set looks to be a bit more complex then that)
So idiots who likely roll DK's will still spec whatever the arms equivalent spec is for DK's, gem for crit and ap or whatever the primary offensive stats for DK's are and will still yell stupidly "LOL IM DPS NOT TANK LULZ"
The ability to tank requires a certain mindset, same as competent healers, and non-retarded dps
An idiot is an idiot is an idiot whether it is at the helm of an arms warrior who doesn't know what avoidance means, or a hunter that rolls on expertise gear or a paladin that gems for spirit.
People who roll Death Knights will be of the same mold which is why when they hit 70 and hit up Northrend a vast majority of groups will wipe in 5 mans.