How about stacking same character on a team will decrease the team damage that got same job

I mean if stacking 4 tank thier damage will drop 10%/tank in team, so they damage will descrease 40% each tank
If 2 mage on team then both mage will got 20% damage decreased, so they wont really usefull on making DoT in clash
While rog got thier critical or damage reduce by 10% for each rog in team

This wont reduce your damage if you disnt have same job on your team so your damage wont get reduce