Warlocks are a really cool class. They have been heavily impacted by various code changes over the years. When I started playing SK they sucked pretty bad, but over the years they've been one of the classes that Dulrik has actually tweaked and worked on a lot. A while ago they were pretty buff, but now they do seem to be lacking again.
First off, anybody who compares levelling a warlock to levelling a priest has not played both of these classes to any comparable degree. Priests are MUCH easier to level. Spear of faith blows lightning bolt away, especially for levelling. Harm is better than any of the warlock's damage spells. Enchant + brew is beyond any non-combat levelling available to warlocks, rez beats breath of life, and the priest healing spells blow healing rays out of the water. Even the priest's protective spells are superior to the warlock's.
The throw change with NPCs has been a hit from the nerf-bat for warlocks (and all mages)
Changes to how damage is calculated & stuff nerfed magma cling
Earthquake is totally cool in concept, if you can't use it to level the way you used to, then that's kind of lame, IMO. I mean, yeah, you could make an argument that it was kinda broken, but the spell has always dished out utter crap for damage and has always been mostly useless for PK. The main thing that really made it cool was its usefulness in levelling. Having lost that usefulness, it needs something. It should be reconsidered. Keep its uniqueness, but give it some renewed purpose.
I've always loved fireball. Still do.
Healing rays rocks.
Stone skin is pretty cool.
Ironguard was completely fuxxored in the single LAMEST nerf bat taken to the class when the spell was changed. That was just plain stupid.
Burning hands is pretty cool, mainly because it's group effect.
Shocking grasp is kind of lame, a weak damage spell to be immediately replaced by lightning bolt- a damage spell of the same elemental type? Maybe it should be replaced by a spell based on one of the other elements.... I haven't been plugged in to the cabals lately, do the druids have a spell linked to a certain kind of "wind"? That could be a cool warlock spell.
Though it's another totally cool spell in concept, chain lightning generally kinda sucks. The damage of the reflected lightning bolts does crap for damage. And, as stated countless times over the years, it should NOT damage air elementals, given that is precisely the damage type that air elementals dish out. If anything, they're actually VULNERABLE to lightning damage, unless that curiosity has been fixed in the past couple years.
Cone of cold is kinda cool, but it needs something more too. Maybe it could be tweaked to work similarly to magma spray. Let the cone of cold "freeze" to the target, basically coating him in a layer of frost, causing extra damage with the cling, and a tiny bit of cold damage with passing rounds.
This could also work with magma spray to create an interesting effect specific to warlocks. After "freezing" a target with the cone of cold spell, the warlock could then start flinging magma at his enemy. If the warlock hits with a "clinging" magma, the drastic temperature change suffered by the target could cause the magma cling to do like double damage.
I love warlocks, always have. I think it's pretty universally understood that they are not currently up to par. There's any countless number of ways they could be tweaked. Any way they're tweaked, I hope would be done by making them even more versatile and unique to play.