WHM is the new tank! AWWW YEAH!!!?!?!1one!
in multiplayer games tanks can serve a number of functions. but the primary function of the tank has always been to control the field of battle.
To use League of Legends as an example: tanks in this game primarily function as initiators. they run in first. take the brunt of the damage, often dieing in the process, and allows their damage dealing classes to do what they do best: deal damage. Tanks also have a lot of crowd-control abilities to allow them to disrupt enemy DDs and prevent their own DDs from dieing too quickly. It's purely about being able to control the field of battle through disrupts.
but that is a purely PvP environment.
in a PvE environment the game changes slightly.
the holy trinity of gaming is tank/DD/support. there's a reason for this. It's fun. It allows people to do what they like to do. if you remove one of those (tank) then the other two must pick up the slack. it's no longer DD, it's DD/tank because you have to worry about taking damage.
EVERY thing you've said you want tanks to do fall under support. buffing, healing, debuffing, are all support roles. Tanks are there to control the field of battle. DD are there to kill stuff. and support are there to enable DD and tanks to do their jobs better.
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back on topic:
I personally would not mind doing away with +enmity. I can see it's merit, but on PLD currently there is a big modifier to hate generation based on MND. making +enmity less important on PLD in comparing it to WAR. WAR has no modifiers to hate generation, and relies more on direct damage than PLD. so +enmity is more important to this class.
the biggest factor of tankyness right now is dLVL. that being said when fighting things that matter, dLVL is so high VIT and DEF do nothing for you. all you need is lots and lots of HP.
really the damage formulas need to be tweaked, and dLVL needs to be seriously revamped or removed from the equation.
it really doesn't have anything to do with +enmity. it's jsut a fault of the current formulas.
Ahhh, but this is an assumption. in SWTOR tanks can 'provoke' an enemy and reduce their damage to allies. +enmity could affect this. more enmity means a longer duration to a debuff or potency of a debuff applied when tuanting/provoking.
hate threshold could also balance how much damage you do, making -enmity worthwhile. as you hit an enemy they resist your attacks more and more due to hate threshold. an enmity dump could be used to reset this. and -enmity gear could delay how long it takes you to reach this cap. there are many creative ways to use the mechanic in PvP.
right now hate=damage. until the formula changes this will be true. the best PLDs I've seen have capped (or better) STR/MND. and the same is true of WAR with STR/VIT. efficiently rotating abilities is what differentiates the good from the great.
PLD already functions like this to a degree. MND plays a role in modifying an enmity multiplier for combos. It could be easy to add a MND based multiplier to PLD abilities and a VIT based one to WAR. I'm not against this.