This build isn’t great. In these forums, it would not be up to standard.
The only reason why you might choose dervish over warlord for shielded retal is for resistance reduction from Night’s Chill. And they don’t even cap it. They also max first nodes of dmg skills trying to make a retal/regular hybrid for which there are evidently no points. Devotions are also questionable - especially the bindings - as are components, some gear choices (Viloth rings instead of Creeping) and extremely low resistances.
Dervish is not great for retal. Defenses are bad (compared to other classes). Nightblade’s defense specialty is dodge and fumble - avoiding getting hit - so you either don’t take it and be a sitting duck or take it and gimp your retal dmg output.
As Nery said, with Dervish you can get in endgame farming shape (Crucible and low SR) easiest with dual wielding acid. This is dervishes main forte.