Warlocks didn't have volley, but they had counterspell. Less good in that it can't backfire on the original caster, but superior in that it works against people already fighting you, and also protects groupmates. Ok, it could be used against you, but that almost never happened.

Then there was the ability to make a room anti-summon, and (if I remember correctly) prevent evil servitors entering it. Pretty nice if defending a cabal inner or outer against a conjie.

Then there was the ability to make a ward that blocked some blows (along the lines of parry and dodge).

All in all, a nice skillset for dealing with scions. Would I rather have scion powers? Yes. But Warlock powers were a nice foil for scion powers, and they had the parry-ward thing so that ragers didn't slaughter them.