I have the 4set bonus that reduces the cooldown of Dark Soul, and use it combined with Synapse Springs for Chaos Bolts but because of the difference in cooldowns I generally end up leaving Synapse Springs unused for about 20 seconds while I wait for DS's cooldown.
Over the course of a boss fight that amounts to quite alot of lost uptime. Is it really worth it when I could just use it as soon as it's ready?
Do you think that's cause enough to use the Glyph of Dark Soul?