I know there are alot of these threads, but this isn't about numbers, or 'viable' vs. 'meta', this is about the true identity of WHM and how the changes in 4.0 (as we currently know it) activity work against that identity.
To me, more than the ‘pure healer’, WHM has always been the ‘simple healer’, with straight forward abilities and simple buffs. It is this identity of being simple, powerful, and fun to play, that first attracted me to WHM in 2.X, and kept me attracted to WHM in 3.X. 4.0 destroys this identity...
With the Lilies mechanic, not only are certain WHM abilities now tied to RNG, but certain abilities are now also mutually exclusive; if you use one, you lose bonuses to others, if not getting locked out entirely, and are reliant on RNG to get them back. This is the antithesis of simple, and simply not fun.
The Confession mechanic is arguably worse, as far from giving you a nice bonus, it is not only RNG based, but also a gate on even being able to make proper use of certain abilities. Again, this is the antithesis of simple, and simply not fun.
And perhaps the worst part; neither of the other healers have any such limitations on their core kit:
Like the WHM of 2.X and 3.X, (once in a stance) AST is free to deploy their full healing kit at any time, and nothing has changed in this regard for 4.0. Also, with the changes to Cleric Stance, it makes Gravity far easier to use than Holy, and frees up mental space to pay more attention to the RNG based card mechanics.
SCH is slightly more complex, with a stack mechanic that does make some of their abilities mutually exclusive. However, as there is no RNG involved, and all these abilities have a predictable and relatively short cooldown, as long as the SCH plans ahead (which ties very well into their lore) this is far from a detriment, and indeed makes the SCH very versatile.
Lastly, both AST and SCH received good, identity re-enforcing changes in 4.0, all while keeping (indeed, even expanded upon) their vastly superior utility. Meanwhile, WHM not only had its identity further stripped by putting a number of previously unique WHM abilities into the cross-role system, if not removed entirely, it gained absolutely nothing it needed in return (quite the opposite in fact).
So, you can ignore this if you like, but those are my reasons (far more so than not being 'meta') for quitting WHM come 4.0, and nothing short of restoring WHM as the ‘simple healer’, and giving it the improvements it so desperately needs (i.e. useful group utility), is likely to be anywhere near enough to change my mind.
PS. Unless crowd control is making a major comeback in 4.0, why the hell does WHM still have Repose?