One of the most important things to note about Lucario "counter" is that it is actually [if what I've been told is correct] the best combo-breaker in Minus... I was told it's invincible frame 1, so if that's true, it's not only faster than even mashing airdodge would be if you could airdodge out of tumble, but you can't airdodge out of tumble, meaning it's the only way to become invincibile without either wiggling out of tumble and airdodging or burning a jump and airdodging [which are both still slower].
As Falco, to try to avoid followups I sometimes mash jump and dodge and will avoid a followup [useful notably against ROB's laser if he isn't quick in using it after a strong hit], but Lucario and just mash down+B to achieve the same effect... while still controlling what direction he moves afterward AND getting a hitbox after the invincibility, something mashing jump+airdodge can't match.
I honestly wouldn't mind a jump-cancel ON HIT if the point of the cancel was to extend Lucario's offensive game [that is, make it some sort of whack but cool combo extender], but the JC is way too safe and the grab cancel makes shielding it less effective [not sure, but I think JC side+B didn't work to grab people who shielded it]. As it stands now, the move is just basically among the best in the game [it rivals Sheik's 3.Q vanish in terms of safety and ease of use].
EDIT: Also, I personally think counter shouldn't be a kill move... sure, countering a lot is annoying, but dying to counter at like 110% is SUPER annoying... reduce the KBG and divorce the move from aura if we want it balanced, ESPECIALLY if it keeps the cancels [although if it combos into stuff then... that only sort of fixes the issue...]