Tanking is a geometry puzzle. You’re balancing leash ranges and positioning, thinking of ways of getting split ranged mobs together. I like to dive to the farthest extend of a monster’s leash range and get as many of his friends together as I can and then double back to my healer while kiting melee mobs around to the ranged mobs.
You don’t really need any addons to tank, you just have to think of tanking as what tanking is supposed to be.