The problem with speed is that it greatly restricts classes that get to do BIDs because it would always consist of a tank, healer, karma, poko, and buffer (CCBD) or DPS (usually Turtle or Fighter). Any other class was basically a wasted slot, which is stupid. Also there's hardly any strategy around it. Just keep the Tank alive and have its Attack Speed buffs fresh while it murders the boss.
this does not change the fact that speed is optional, simply, if they want to do in the critical, just do, Kinswkk Is an example of this.