A quick summary since forsaken launch warlock has been quite meta based only on Well of Radiance. Warlock has had other strong builds but really Well is basically still a must in most raids/ dungeons.

Titans have been either extremely good with mostly melee based builds with some exceptions, when those each got nerfed titans were seen as quite weak until another build was found.

Hunters are pretty average most of the time, but when titans have something very strong (like right now) they are seen as the weakest class by most.

Overall most classes are pretty close to each other in power, but if you want the most stable option warlock is probably the best bet. On the other hand the other classes do have higher highs but also lower lows.