It depends. If you have 2 healers and one of them dies, its the other support's fault because support is the #1 priority when healing. If your tank is overextended without their team then theyre feeding and thats only their fault. If the dps is trying to go in and get kills but dies for it then that could be the tanks' fault for not creating space. It really depends.
Traditional mmo logic is because of threat percentage based aggro though. You literally won't pull off the tank unless you're hitting the wrong stuff and the tank won't die unless the healers don't heal enough
Doesn't work like that in masters... If the tanks die, it's the healers fault. If the dps die, it's the healers fault and if the healer dies, it's the other healer fault.
No the healer should do their fucking job and heal me instead of walking past me while I'm at critical health and standing right in front of them so they can pocket the person in their group even tho they are playing like total shit