As noted, this change is an improvement to AOE SUSTAIN in pve mostly.

And it's a SLIGHT improvement to MT situations where you have enough mana that you can sustain your DPS while using boosted DEFENSIVE cooldowns.

For OT and PVE it's not an improvement in OVERALL dps, but allows for centralizing potential burst via DACNS-DASE.

In the end I'd have preferred a decrease in cost as opposed to a cooldown reduction, but you gotta take what you get sometimes.