#1 - May 4, 2016, 6:10 p.m.
The biggest part of the problem comes from tanking lots of mobs, if there are more than 4 or so mobs they start spreading out around you, this is highly disruptive and creates some issues. This first issue being that they are outside of your frontal cone for cleaving. The second issue is mobs that are behind you cannot be parried/blocked/dodged etc... So what this creates is an issue where tanks have to consistently move around in order to keep the mobs in front of them.
To fix this simply allow mobs to stand on top of each other. With the way loot works now it wouldn't be the end of the world if mobs died on top of each other because corpses share loot tables now and corpses disappear when skinned/mined/picked etc... so it wouldn't effect gatherers either. I suppose the other alternative would be to make it so they still move to find a free spot around you but make those available slots smaller so more enemies can gather around your front side.
Now for the second issue at hand that isn't as much of an issue, but still happens. A lot of bosses in dungeons and raids freak out if you even take 1 step away from it, they don't simply move towards you for that 1 step... instead they either start freaking out and doing a little zig zag until it finds a valid position or even worse steps inside of you to where it gives you the error message "you must be facing this mob" which means it is technically behind you and you have to reposition yourself yet again hoping that the mob steps towards you correctly this time.
I'd assume the biggest thing that causes this is the mobs/bosses that have smaller hit boxes as I don't see it happen as often on larger bosses with big hit boxes. So I suppose making sure bosses have a large enough hitbox even if they are a smaller model would hopefully fix this issue.
Either way these are just quality of life improvements, but it would still be nice if it were fixed for Legion. Thanks.