The thing is, cone/circle shape is irrelevant to positioning. Due to the way mobs try and glue themselves to the player, once the circle AoE tank grabs aggro, all they have to do is move to the farthest target and bam, all the mobs will be clumped up on one side of the tank, where the circle can still all hit them, with all the enemies facing one general direction exactly the same as the cone.
Cones had their own advantages such as reach, being easier to pick up spread out groups, or that they made you move more, thus keeping you a bit more engaged, but let's not pretend they were somehow 'better' for positioning. Any tank worth their salt could do the exact same thing with circles with zero issue. Whether cone or circle, my movement to group up mobs was literally the exact same. It ain't shape focused in the slightest.
Besides, DRK still has line aoes if you want to have fun with non-circle gameplay.