So I have this idea for a great concept, this may come out a little akward so I will try to explain it, so its somewhat understandable.
The idea goes like this: Before you start an encounter, everybody signs up as their role in the raid (tank healer or dps) just like with the random dungeon tool. Now, you might ask yourselves why?
Instead of the boss targeting a random raid member, the boss now knows who is who. This means the boss can now throw specific hazards at specific players, lets have some examples (bare in mind, these are BAD examples, and are just here to illustrate and explain the concept)
Tanks:
The encounter knows who are tanking, why not cast an undispelable sleep on one of them? So the other tank have to pick up what ever the other tank was tanking for say 15 seconds. If this was thrown on a random raid member (a 15 seconds sleep) it would either be a small DPS loss, or another healer had to heal some more.
Healers:
Again, the encounter knows whos healing and whos not. Lets get some mana leeching going! So that, well timed innervates, holy hymns, mana tiddes would be very nesccary. If this was cast on a random member, maybe a mage. A simple evocation would be needed, and you would be good to go again.
DPS:
The encounter is able to pick two specific DPS and throw them into a big chunck of ice (much like on the LK encounter in frostmourne) and they would have to free eachother by DPSing something down. The timer can be much more shorter because the encounter knows that its two DPS, and not a rogue and holy priest (poor rogue, having to be saved by a holy priest )
The idea is to give the encounter more options on what to do and what not to do. What spells/abilities/obstacles hurt what roles the most, to give even more challenging content.
TL/DR: You sign up before raids as your role, the encounter knows who is who. The encounter will make whatever you are doing harder for you, instead of everything being random.