Basically so you cannot exceed at both. Imagine leveling 1 class and being able to effectively heal for sch and dps as smn, so in a duty finder with 1 class you can que as either. Meanwhile other players are forced to really play as what their selected class is. Bottom line SE does not want you to kill 2 birds with 1 stone. Anyway int and mind are slightly useless stats imo. With every int increase as a mage your dps barely will change by any means and same goes for mind, your heal without 30 min will drop maybe 40 points, but sch is a crit oriented healer so big deal about you base heal losing 40 when it does not crit. With crit heals granting a broken barrier it does not really matter if the barrier has that extra 30 mind on it, since it will only mitigate about 100 more damage. Basically just choose 1 to stat or stat it with all vit or vit/pie because again that extra 30 for either class is a debateable increase.