You may be wondering why many have replied why sch shield stacking is op, kills the need for whms n all. Well I will elaborate. A well timed adlo and whm stone skin can allow a tank to completely bypass a stack mechanic. This was apparent on some fights and before everyone got lazy on turn 2 and do enrage, there were groups who have timed this combo so well 1 tank could go through most of the fight without ever getting a stacking debuff from the bosses. this also worked on titan ex. Sch synergize with warrior tanks big time and if aldo were to stack the shield a warrior tank would get will cause some mechanics to fail and groups favoring 2 sch and warrior tanks over any other combo.