The titan was unbeatable for two reasons, one of them directly related to the gimmick.
First, his damage output was too high, especially in comparison to level 10 characters without 28 point builds, constitution tomes, or +5 con items. He casts energy balls in blasts of 3, and it only took an average of 2 balls to kill any single player character, except for the most extremely hitpoint-specced. The nerfed titan had his damage cut down so that a typical level 10 cleric could expect to survive splash damage from 3 shots in a row.
Second, the lasers and pillars required stringent accuracy. When the Titan was originally released, you could drop a pillar right through him and he wouldn't fall down. But if he did fall down, you could shoot a laser right through him and nothing would happen. In the nerfed version, the collision area for the Titan has been hugely expanded, so you only need to get the pillar or laser in the same general neighborhood for it to count as a hit.
PS. I will note that the originally released Titan could have been reliably beaten by a 10+ man raid of level 11 characters, if the level cap hadn't been 10 at that time.