TBN if reworked to not punish (Grants Dark Arts, by the buff timer running out, and/or shield break) and rewarding DPS is fine, that's not a problem at all, can be shared. I am only against self only abilities and rewarding DPS gains for it. Though the cooldown may have to extend.
We have Intervention anyway, it has the same additions Sheltron received, extra 10% if Rampart, or Sentinel is active, can only be used on team mates, not self. It's pretty fair.