Unmarked spoilers of the book ahead!
Only long-time Tranquil suffer ill effects upon being curedPharamond was a Tranquil for a long, long time before discovering the cure, so he has forgotten everything about how to keep your emotions in check, and they overwhelmed him. In DA2, Karl (a recently made Tranquil) displayed no excessive emotionality during his brief reversal under Justice's influence. Which leads to conclude that if Pharamond's cure is applied to a recently Tranquilized mage, the process will be reversed with minimal negative consequences.
Evangeline will be able to cure the Tranquil by touchAssuming Wynne's Spirit of Faith now inhabits Evangeline's body, she essentially has a very powerful spirit on speed-dial, and now that she knows about Pharamond's cure, she can probably learn to channel said spirit to touch the minds of the Tranquil, similarly to how Justice temporarily cured Karl in DA2. Only Anders didn't know that the cure could be made permanent. Unless, of course, it is required that for a permanent cure, the spirit must touch the Tranquil mind from the Fade, which would essentially force Evangeline into a Heroic Sacrifice (again) if she ever decides to carry it out.
- In the course of Dragon Age: Inquisition, it is learned that Seekers are also merged with a Spirit of Faith. Seekers don't seem to be able to undo Tranquility by touch. Both Eva's and Anders' cases are special, though; they were not rendered Tranquil like the Seekers are, their own souls are not cauterized and thus are independent on being touched by a Spirit to feel. Or, possibly, the Seekers do not know they're able to do this.