Look - I'm not trying to pick a fight. I was a bit overzealous in my dismissal of it being latency.
I should have said probably and I don't think it is, or I think it's unlikely. I still think that there might be
a remote possiblity, the teensiest, weensiest chance that it might not be latency.

Yes some mobs move. Mainly the ones that snare and run to range. With my tank I tend to have the aggro,
so I can either shift form if on the druid, or wait the root effect to drop and then go get the mob.
(dragging any other melee guys along too).

Some mobs knock back - but most of the time my tank has aggro and the mobs go after my tank,
so if i know a knockback happens I will tank that mob with my bear facing my alts.
If it does an aggro wipe as well (mainly elites in instances) then I'll run back in and taunt it.
Get it under control and reposition it then bring my alts in again.

Occasionally (a mob is positioned in amongst my group). If they cant hit it I can generally just back them up
and then tap follow and attack to get them back on the mob I want, or again if i don't want to back them up
i can have the tank move the mob and bring my team in again (and they are facing the mob).

I honestly believe that having one character who holds the aggro makes position juggling simpler.

I actually agree with you - and as I said before will be going for click to interact.
Being able to send my alts over to deal with a ranged caster while I'm dealing with the melee,
would be fantastic. And the click to interact will stop me having to do any of the positioning tricks
I used to solve the issues previously.