I'm on a PvE server, you would be surpised how many tag themselves in front of a team of 5 and jump up and down.
I have to admit, the first time I fried one of these guys... I laughed so hard I had tears in my eyes.

The other thing they do, is have a hunter drops snakes when your warlock pets is attacking something.
the pet AoE tags you PvP when it kills a snake. They would wait until I had pulled something to attack.
I was playing 5x warlocks and killing elites several levels above me ( so I needed most of my attention ) and I usually could kill the elites and all of the team that had attacked me.
They did this several times before giving up... lots of fun for me