"[Dev suggestion] More strict stat checks when entering duty finer/tutorial tests
Notice I said stat checks, not gear level. It is too easy to bypass the gear level requirement." (from the opening post)

You started completely off base with your dev suggestion. At least you are starting to get to the real problems (manipulated iLvl avg, rotations, DPS taking avoidable damage). BRD using Det is not one of those problems (not even close).
Sort of sounds like mismanaged pulls to be honest (tank not adapting to the dmg output of the party). Healer is usually the one person the tank asks about bigger pulls. Next time maybe your friend can ask the tank to back off a bit on the "mega pulls" if the healing required is overwhelming her.

Maybe if the Devs introduced an out of combat heavy effect for the tank that was based on healer MP level... (joking, but sort of not).