Hey,
This is a stupid little trick, but while raiding I often hear tanks saying they can not get close enough to mobs or pull aggro because too many people are in the way, same deal with melee dps, because truthfully raiding is messy now.
So here's some common sense that most people might overlook. If you down one mobs only to be blocked off from the next mob in line during a raid, crouch down, wall through the healers and rangers, pop out and bam! your in place to smash face!