Such DPS abilities are nothing special in URF modes, hence it really doesn't sound amazing.
Just a wild guess, but I wonder how is a cancellation of(i.e. reactivation and refund times) affected by the special mode's CDR. If the cancel time was affected as well, maybe switfly alternating between -cancel- -cancel… could yield a bursty DPS by proccing more ticks? But that could be just a buggy behavior.
Anyway, did you check guys' runes? They can increase burst a lot too.
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