1. Hots - while they can be efficient and powerfull - need time to do the job. in scenarios where alot of healing is required, you need ogcd heals to make a hot-healer work: something like "removes all hots and grants healing equal to the x% of the hots heal-effect"
which would actually fit WHM pretty good. The mainproblem is: there must be a constant need for healing and comparable big hp-pool to make hots work, or else its just useless overheal.

2. direkt heals are simple - they are the go-to- tools of most healers so everyone need at least a base amount of them, in case their other tools dont work. the more hots/shields/fairys/totems/or whatever you got, the less dh you need and viciversa...

3. Shields are basically direkt heals with the disadvantage of a greater chance of overhealing (because their duration can run out etc.) but with with the big advantage of keeping people alive even if something goes wrong.
they are hard to balance, because if you make them to strong no one will take WHM over SCH :P so you would need to limit their use like " cant be reapplied for 30sec" and add more direkt healing in order to close the gap.

4. all pets, totem, ai´s or whatever are basically stylish hots that can die. they have the disadvantage of a more or less capable ai and the advantage of a more or less capable ai.
the worse your ai, the slower your pet reacts, the more healingpower and dmg-reduction is needed for them to be usefull.

5. Healing- via Dmg need a capable ai to, because you would have the switch targets ingredible fast to make it work otherwise. also you need some sort of buffer, that lets you charge up your heal and use them the moment you need them, or you have all the problems of hots again. also you would need a specific minimum amount of dps to clear content , which could also make WHM less competetive again^^

6. while nice and edgy it has several disadvantages that makes it VERY errorprone: like all mechanics that reduce you to 1hp.

7. buff-healers are... well it depands on the buffs, the more buffs you can give others, the more valuable you are, with the potential of making all other healers useless. therefore their playstyle would revolve around sharing a limited number of buffs with partymenbers.


right now the mainproblem is more the low healingrequirement (also due to the heavyly skripted fights) where you need powerfull heals but only once a minute.
this gives healers with buffs, pets and shield the advantage over heals with high direct heals... hi WHM!...

in order to make more room for different healers you would need to randomize attackpatterns, ingrease hp-pools and increase incoming dmg over the raidbuster every 60sec that eos can take care of herself while i can keep spaming broil2 - i miss my HW-dots -.-