Disturbance/Lightning Strike is functionally the Sage/Sorc's "basic attack" (yes, it costs Force to use, but it's a pittance). It does pitiful damage because it's not supposed to be a heavy hitter, like Charged Burst, which, rather than being a basic attack, is a basic resource consumer. Sages/Sorcs, because they have comparatively massive resource pools compared to everyone else in the game, have a different paradigm for their abilities than pretty much every other AC out there. As such, their "basic attack" is a cast time ability that consumes a modicum of Force. That's just how they work.
Then the power shouldn't have such a high cast time. 1.5 sec is an eternity in this game. It really should be an instant ability. But better IMO for Sages/Sorcerors to have a basic "burst" ability.
And as a 'basic attack' it also fails because Seers and Balance specs really don't get anything from using it at all. Balance's spamming attack is TK throw.