Just to toss out another comment about marking.
As a tank I don't always mark target. If I don't mark a target then I don't care which ones you focus on, I'll hold hate on all of them and if I loose hate on one then that is my fault.
If I specifically want a certain mob to go down first then I'll toss a 1 on it before I pull.

Only other time I mark targets is if a party member specifically requests me to do so. I had a guy ask me to mark in AV when we reached the first boss, so after the boss was dead I marked each pull. I would mark 1 first, pull and then mark 2 and 3.

Marking is not hard, but it's tedious especially when you've ran the same dungeon a dozen times and for the most party people should know the kill order. It's only really beneficial when there's a new person in the dungeon or someone who doesn't know all the pulls yet.