I use an add-on called AutoTarget (
http://www.curse-gaming.com/en/wow/a...utotarget.html) that will lock on to a target just mousing over them, without clicking, if it matches certain configurable criteria. I really only use it in pvp, have it set to only lock on when the target is pvp flagged, hostile, and over lvl 56. Allows me to just swing my mouse over that sprinting noggenfogger'd gnome rogue and have it targeted, without timing a mouse click on those 4 pixels.
I have long given up on tab targeting, especially in pvp, as it will never target the healer in the back of the group.