There really isn't much incentive to use True Strike over Twin Snakes until you have the Skill Speed (430+) to alternate safely. Losing Twin Snakes even for a few seconds hurts your damage far more than missing out on 10 extra potency. I wouldn't go so far as to call True Strike "useless", but it's certainly a strange design choice to require you to be decked out in end-game gear to make efficient use of a skill you've had since level 2.
