Victim said:
Yeah, and a normal 15th level arcane caster also 2 shots the enemy sorcercer with Scorching Ray. The lesson here isn't "Warlocks are overpowered," it's "d4 classes need to boost their Con scores." How many 15th level characters can't do 52 damage given almost 2 rounds in a row?
Assuming the Sorcerer does not have some form of protection from fire (or globe of invulnerability up or spell resistance up) at 15th level.
There are very few protections from (higher level) EBs except spell resistance and even that can be sidestepped by Vitriolic Blast (doing 13D6 average instead of 7D6 at 15th level). Concealment miss chance (or equivalents like Mirror Image) is also helpful against it.
But, he can do Eldritch Chain Vitriolic Blast for 13D6 against up to 4 targets (eventually, 7D6 on round one, plus 2D6 for 3 rounds after that). Every single round. No save for half damage. No spell resistance. And a fairly high chance of success because it is a ranged touch attack. And if the ranged touch attack against any of the targets is in his threat range, a very good chance of doing 26D6 (assuming no way to get the acid off or neutralized) against that target. Now, the acid damage can be minimized with Resist Elements Acid (or even neutralized with Protection From Elements Acid for a short period), but this is still more potent than Scorching Ray (or even most area affect damage spells in most circumstances).
13D6 can take out a Barbarian in 4 to 5 rounds. A high CON wizard in 3 rounds (since he can do 7D6 on round one, 9D6 on round two, 11D6 on round three, up to a maximum of 13D6 on round four if he keeps hitting, but the overall average will still be 13D6 per round). Plus, with the extra acid on later rounds, opponents tend to die if they fall unconscious unless they get help.
Granted, there is only a 4.75% (5% * 95% chance of making the threat roll assuming a 95% chance of hitting each of their touch ACs) chance of doing 26D6 this way per target, but when firing at up to 4 targets per round, the odds are in your favor that it will happen in maybe a third of the battles at least once (the odds in one round with 4 such targets are 4.75% + 4.5125% + 4.286875% + 4.07253125% = 17.6% or one round in six).
Btw, at 16th level he can Empower Eldritch Chain Vitriolic Blast 3 times per day and do an average of 19.5D6 against up to four targets (39D6 if he criticals). Imagine this in a surprise round by the NPC Warlock. Four PCs have only taken 38 points of damage on average (assuming he did not critical any of them), but they have 3 more rounds of 10 points each round and if he wins initiative, the NPC Warlock can do it a second time before any of the PCs can react. That's 86 points of damage per PC and still more to come. Mass Cure Critical by the PC Cleric, and even then, the PCs are in trouble (unless the PC Cleric is 17th level and can do Mass Heal).
Plus, Warlocks at 12th level can make virtually any magic item they wish.
The jury is still out, but with a good set of other invocations, I can see a Warlock as a killing machine. Plus, I consider them more potent at lower levels than higher levels relative to their level. The chances of them surviving to get to higher level seem better than most other classes.
However, I do see your point. It takes time for him to dish out his damage and some other arcane spell casters can dish it out a little bit quicker (abet with saving throws and spell resistance rolls). But still, ...