Seems like Spriests need a good overhaul. A lot of people are calling for the removal of voidform and replace it with a more bursty, less rng mechanic.
I think all they need to do is make
Lingering Insanity and
Surrender to Madness base abilities at a higher level. But give Surrender to Madness less of a drawback, but also a little weaker.
Compare the Fury Warrior ability
Recklessness, this is a very strong ability, pretty short cd and ironic to the name has no drawbacks. Surrender to Madness is different, it is bad in groups because it puts a strain on your healer at the end of your buff, and risky in solo because then you need to heal yourself. The only benefit it is very strong and lasts a long time.
Instead make Surrender to Madness reduce healing received by 50% and cannot generate insanity for 10s, but increase insanity generation by 100% and can cast while moving for 30s. 2min cd.
Still a useful ability for burst situation and long battles without worrying about the downside outcome, while not being such a strong ability that would only justify being a talent. Since that talent space still needs to be filled, just make a talent that buffs Surrender to Madness to be competitive against Dark Ascension and Legacy of the Void.