When you have aggro from a mob and you for some reason need to buy some time (or loose aggro completly) you can start walking backwards and slightly turning left and right as you go. Dont strafe but walk (use the A and D button). This will make the mob go slower and if you keep walking it will eventually stop attacking you.
Its not however fool proof. I looks as though it just works some times, so dont count your HP on it
This can be usefull for many different reasons, but I find it really good when using it with a shammie while youre waiting for your cooldowns.
Don't know if that helped or was usefull to anyone, but hey. Just trying :P