There is a difference between interrupting the flow of a rotation due to an arbitrary mechanic like Enmity and something that can be planned around, like an extra ADD.
However, talking about enmity, I haven't seen a solution for displaying Enmity in a clear way that can allow you to effectively 'tow the line' on keeping just enough enmity to keep it, whilst still doing as much DPS as possible.
As for another point, why should a tank do the same level as a DPS? The only point this has even happened is WAR in HW, otherwise all tanks have had lower natural DPS than DPS. It also feel weird trying to compare a tank's DPS to a DPS' DPS and saying they are 'artificially capped'. You should be comparing a tank's DPS to other tanks, not DPS.
However, if you do want them to do DPS levels of DPS, and having their main role supress that, what about healers? Should they do DPS levels of DPS where the healing 'gets in the way' of them attaining that desired maximum? I know you don't as you have already described this as 'Healers getting it right', when, ironically, losing a GCD in order to heal is the lowest thing on the priority bracket, focusing on using the oGCDs first.
Also, if tanks can do DPS levels of damage, you will just bring a party of mostly tanks. They do the same damage as DPS and have much more survivability, which means there is going to be less burden on the healers. This is the main reason why tanks have to do less damage than DPS.