Currently in Classic, Heroic Strike and Cleave do not consume Flurry charges while in vanilla they did, as proven by multiple examples from a 1.12 video below.
First the bug, as shown by the following abridged log excepts:
9/16 18:07:28.525 SWING_DAMAGE (Melee swing, crit)
9/16 18:07:28.834 SWING_DAMAGE_LANDED (Melee damage applied, crit)
9/16 18:07:29.240 SPELL_AURA_APPLIED (Flurry gained, 3 charges)
9/16 18:07:30.082 SPELL_CAST_SUCCESS (Heroic Strike cast)
9/16 18:07:30.452 SPELL_DAMAGE (Heroic Strike damage applied)
9/16 18:07:31.472 SWING_DAMAGE (Melee swing, non-crit)
9/16 18:07:31.680 SWING_DAMAGE_LANDED (Melee damage applied, non-crit)
9/16 18:07:32.071 SPELL_AURA_REMOVED_DOSE (Flurry charge removed, 2 remaining)
In the log above the player crits a normal melee swing, gains Flurry, lands a non-crit Heroic Strike which doesn’t consume a Flurry charge, then hits another regular melee swing which does consume a charge.
9/11 17:19:36.667 SWING_DAMAGE (Melee swing, crit)
9/11 17:19:37.065 SWING_DAMAGE_LANDED (Melee damage applied, crit)
9/11 17:19:37.470 SPELL_AURA_APPLIED_DOSE (Flurry refreshed to 3 charges)
9/11 17:19:39.277 SPELL_CAST_SUCCESS (Cleave cast)
9/11 17:19:39.504 SPELL_DAMAGE (Cleave damage applied, non-crit)
9/11 17:19:39.504 SPELL_DAMAGE (Cleave damage applied, non-crit)
9/11 17:19:41.899 SPELL_CAST_SUCCESS (Cleave cast)
9/11 17:19:41.934 SPELL_DAMAGE (Cleave damage applied, non-crit)
9/11 17:19:41.934 SPELL_DAMAGE (Cleave damage applied, non-crit)
9/11 17:19:44.784 SWING_DAMAGE (Melee swing, non-crit)
9/11 17:19:45.166 SWING_DAMAGE_LANDED (Melee damage applied, non-crit)
9/11 17:19:45.567 SPELL_AURA_REMOVED_DOSE (Flurry charge removed, 2 remaining)
In the log above the player crits a normal melee swing, refreshes his Flurry charges to 3, lands a non-crit Cleave which doesn’t consume a Flurry charge, lands another non-crit Cleave which doesn’t consume a Flurry charge, then lands a non-crit melee swing which does consume a charge.
And for the vanilla proof (video is 1.12 as evident by cross-realm battlegrounds):
He crits an Overpower and gets 3 Flurry charges, then immediately uses an Heroic Strike that is dodged and consumes a Flurry charge (can see it change from 3 to 2 in his buff bar above):
Crit an auto attack which gives him Flurry, then lands a non-crit Heroic Strike which reduces his Flurry charges from 3 to 2:
https://youtu.be/ISx6eni6I1k?t=186
Crits multiple Whirlwind hits which gives him Flurry, then lands a non-crit Cleave which reduces his Flurry charges from 3 to 2:
https://youtu.be/ISx6eni6I1k?t=440
-magey & the Fight Club team