I don't know why but most of the players doesn't seem to use this particular skill. I first tried this skill in the Hyperion Circle of Slaughter in PT1 after completing the main story and was simply amazed. Pure BA. But as soon as i started TVHM, removed that skill as i was afraid i'll become too much dependent on that skil and make combat difficult once i hit UVHM. I was right. TVHM was difficult and died a few times but mostly because i was not using phaselock efficiently.
Once in UVHM, thoughlock was back on. Yah the added 3sec cooldown delay was there and i could actually feel phaselock cooldown taking that slight bit longer but once coupled with ruin, converge, sub sequence the end result was pure devastation. 1 thoughtlock can take out a big group of enemies in UVHM despite 4X health increase & regeneration. Oh shield too. Backed by me with an Intense Unkempt Harold.
There was tradeoff. I was really used to wreck. Was missing that increase in firing speed and damage but i guess wreck can never ever equal the damage of thoughlock. It works so many other way than just distracting the enemy. Once even tried the Harmony tree just to test scorn. But by then it was too late. Died too fast compared to using thoughtlock & ruin where i died extremely rarely and only if i ran into a firefight with phaselock on cooldown.
But while fighting raid bosses, yah that skill kind of becomes useless. Instead increasing the cooldown. But in most cases, this skill kills. Kills everything except Maya of course.