I actually did not really do anything to that effect of stating when is optimal usage of Lightspeed.

I just stated why any DPS spell with Lightspeed up is a sub-optimal maneuver and also stated that if I happened to have Lightspeed up at a time where I need to do a movement mechanic, I'll probably just keep it up and fire a DPS spell out for the sake of simplicity, even knowing it was sub-optimal. However, the better maneuver in this case is to cancel Lightspeed, use Swiftcast, and fire your spell.

To be honest, in any serious tier fight, Healer's should be mapping out their CDs for optimal usage which would include for times where you're optimally using Lightspeed to get past heal checks then moving back into a position to DPS without Lightspeed up to maintain optimal use of the CDs and DPS up times.