I can think of some other factors to make the idea of sacrificing the buffs to work. Shake It Off would also have to check for the buff timers to determine the strength of the additional effect.

Eg.

If ToB timer is greater than 9s, then
X= 500 potency
Y= 15s

If ToB timer is 1s, then
X= 25 potency
Y= 3s