So now that the PH has been out for close to a week, I'd like to open the thread up to general warlock discussion. Whatt do people think now that we can see all that they can do (and can't do).
Personally, I'm trying to figure out what the warlock's "role" in the party is. They're spell list is kind of wonky, IMO, and they lack a lot of the fun spells other arcane casters get (teleporting and the like).
They do get misty step, which is a 30 ft teleport but you probably don't want to use it if you can help it because....
Until level 11 you are limited to two spell slots between rests. That is a fairly serious restriction. On the other hand the slots gain in power such that they are eventually 5th level. It seems like you'd want to focus on spells that improve/grow stronger when cast at higher levels and on long-duration buffs/debuffs/area spells to really get the most out of this. For example: Hex, Fly, Spider Climb, Evard's Black Tentacles (if Great Old One).
The Patrons offer a few nice spells but the abilities they offer are mostly defensive until the capstone.
The invocations are mostly damage and scouting/utility oriented. The Pact of Chain and Pact of the Blade Warlock could be excellent scouts/infiltrators. In battle they'd mostly rely on eldritch blast (or the the blade with thirsting blade and lifedrinker), with the spell slots used for "oh crap" moments or the occasional well-timed/well-placed megaspell.
The Pact of the Tome seems like he is meant to be a utility caster outside of battle and a Eldritch Blaster/occasional debuffer inside of battle. You can collect rituals from every class and use invocations to further this.
So you might get:
Invocations:
speak with animals at will
detect magic at will
"read all writing"
speak with dead at will
arcane eye at will
witch sight: see true forms of creatures/through illusions
and spells:
comprehend languages
identify
unseen servant
water walk
tenser's floating disk
etc.
This might be helpful if you don't have a wizard in your party and you need some out of combat magic support.
Still, I think the warlock is a bit of an odd bird; if the bard or monk were the classic "5th man" in 3e, I think the warlock fills that role here.