Options to buff Dervish survivability: Eternal Aura

Lower crit damage on the scythe to prevent assassin abuse while increasing the attack speed to compensate You would then still have crits more often on the assassin and increased attack speed for both.

You would then still have crits more often on the assassin and increased attack speed for both. But if you reduce crit damage to 1.25 instead of 1.41 while simultaneously changing more attack skills to remove enchants for their effects, while introducing dervish enchants that can be used during other actions, the dervish becomes usable and superior to assassins, rangers, and warriors with a scythe.

Here's my idea. Aohm-->armor pen
some derv skills into adren req.
Change myst to lower the cost of derv skills and grant armor per level.
Buff pious fury to last double if an enchant is removed.
Convert unused derv attacks into skills with utility.
Lower crit damage on the scythe to prevent assassin abuse while increasing the attack speed to compensate Making dervish attack skills run on adrenaline would either not be worthwhile (the attacks that aren't worthwhile would remain as such) or make them even worse (the ones that currently are worthwhile).

Dervishes have more than enough survivability already. Unless you give them some kind of broken SF-like defense, they will still need prot. And if they are getting prot, then they need no additional defense.

Pious Fury would still be worthless.

Increased attack speed would not help as much as you think, because most of the attack skills worth using already have reduced activation times. A better option would be to raise the minimum damage by a large amount and reduce the maximum damage somewhat.