Quote Originally Posted by Xefas View Post
Well, Warlocks aren't as powerful as a full-caster, simply for the reasons that they can't either 1) Become an unstoppable juggernaut of death or 2) slaughter an entire encounter with one well-placed spell. However, they're still a lot better than fighters/monks.
Debatable, for fighters at least. A decently-made fighter is going to be capable of outputting overwhelmingly more damage than a warlock ever can. Warlocks do have UMD, but overall their other class features are underwhelming. Granted, the fighter will probably only get that damage at close range... but at least he can beat up creatures quickly when the wizard holds them down. In a typical high-level party dynamic, the warlock is just going to be throwing around pings that don't contribute meaningful damage (unless they have a heavy ability-damage focused build, and even that isn't that great.)

Many invocations can be copied by magical items that are relatively cheap at higher levels, and if you look at the high-level ones there's pretty clear drop in power (lower-level invocations often grant spells from around that level at will or all day... higher-level ones are often more along the lines of flavor.)

Much like with the Sorcerer and spontaneous casting, I think what it comes down to is that they overestimated the value of the warlock's all-day abilities.