It's hard to notice this in most content since nothing really requires you to heal extensively, but I just recently completed O8s and this was a consistent problem with WHM only. They build aggro way too fast and easily.
I know a lot of people like to say that this is to balance out them having constant access to Cure III, but similarly on AST, I was able to use all the tools of my kit and spam aoe heals without any risk and achieve the exact same results as a WHM would have without the risk of killing myself from aggro generation.
I'm not saying it should get a static enmity dampener like AST, but wouldn't something like plenary stacks reducing aggro generation make sense? It just seems abnormal that when you really need to push out the heals, you'll probably end up getting yourself killed without the help of a Ninja or forcing your tank to work overtime.
Just my opinion of course, what do other people think? Would lowering enmity generation make WHM too easy? Is it too uncommon of an issue to even bother fixing?