I like the companion concept in that every player character should have a companion in one form or another that has function in combat. That said I do not believe a Tank class should have a combat pet in the traditional sense, nor do I think it should have just a dumbed down version of a pet just for flare.
I don't believe Dire Lords are going to be Necrotic Tanks in the historical sense, to be quite honest from the above-mentioned interview I believe they will be more akin to VG's Bloodmage.
That said, I would rather not see Skeletal Minions and the rest of the Atypical undead Pets found in a lot of games. Rather I would like to see more ethereal magical entities; shades, specters, geists, something a dark mage pulls from the ether vs a necro summoning from the ground.
I think the DL's pet should be more along the lines of a combat multiplier familiar, than a true combat pet with a full up action bar.
Rather it should have a limited action set and have a full complement of passive combat multipliers ties into the DL's bloodletting theme and the type of damage the DL is taking.