To be perfectly honest, this was really only an issue in the early days of ARR when PLD specifically had no aoe tools outside of Flash (which generated crap enmity), got its tank stance at 40 and it's aoe oGCD after that. WAR didn't have issues if they could bloody target properly, though WAR had significant other problems.

By the time mass pulling became a constant thing among the more casual population (Brayflox HM) you only had to worry about double Regen pulls even as pld, so long as you hit everything at least once with flash or hit the lone straggler with shield lob.

By HW DRK introduced the Sprint pull, being the only tank with zero need of TP to effectively pull and having an evasion boost to ease dmg during the pul and the onslaught come the stop. Enmity by this point was a no brainier. As long as you had your tank stance on...which you should during dungeon pulls.

Stormblood was much the same as HW for enmity and pulls. It didn't get harder at all and come ShB there's no excuse in the slightest for having any amount of enmity difficulty as a tank. As long as you hit enemies once with tank stance on you'll be fine come the end of your pull. If you manage to miss an enemy, your single target ranged attack has increased enmity as an effect.

Failing a pull just because you have regen shows the lack of skill of the tanks part more than on the healers part. Sure, once upon a time if was absolutely detrimental to do but that time has long since past (nearly 5 years at this point).

I'll be honest though, if I hit any ally with an effect and I see you click it off, I just don't hit you with that effect for the remainder of the instance.