Quote Originally Posted by Gemina View Post
but I believe the stun effect remains the same for all.
It does. The only difference will be if someone else stuns a mob first yours will count as the next stun.

Also keep in mind till lv 50 and 60 dungeons you don't nearly outlevel mobs as much as you do after and your experience will pull sizes and tank durability will change drastically in non-levelling dungeons.