[Chaos]

As per PvP's nature, high power is a burden compared to utility. Unless you're going up against a RES tank (and even then, Evoker is given a built-in counter to those), odds are you're not going to miss the loss in power, especially if you're using Sync-Mind skills. As for its HP cost: Screamer --> Parreta --> (Insert 3M skill/spell here, if they don't have Water Resist). Or just recoup with a straight heal, if you have one of the Curate classes equipped. (Pierce resistance has already been covered)

I believe I've stated this before, but while curing silence for 10% HP/1M is a good idea, being able to also take out a skill meant specifically to reinforce Silence with no additional cost is broken. It turns Etacof into a guessing game against each and every spellcaster you encounter. They don't have Screamer? It works. They have screamer? They get 6M to punish you, and a spellcaster has a lot of punishments to dish out. Losing 1 momentum on an action that destroys a locked-in debuff like Silence is a very small price to pay, and even the 10% HP cost doesn't balance it out. (Unless you're rolling a Hyattr spellcaster, the mage's HP can easily be fully recovered after a decent Paretta or a simple Graft)

Again, like I've stated before, Screamer needs an additional cost when taking care of Etacof. Something like Kam suggested should be fine.