The cooldown (60s) on Momentum Swing (LD Tier2) has a 15% chance to reset on Cleave/GCleave. It does appear to be working, however if a second Cleave/GCleave procs another reset before the Momentum Swing is used next, it actually seems to reapply the cooldown timer. Exposing Strike (Core 3 DeS) also seems to reapply the cooldown timer sometimes. So, if Cleave, GCleave, Exposing, and M.S. are in one's melee cycle, it's often the case that M.S. will go back into cooldown before being used.