While you're being facetious here, that isn't actually a bad idea, conceptually. Fighters used to be able to basically kill one 0th-level enemy (i.e. the vast majority of NPCs) per round, and that wasn't a problem. Since you want to hear peoples' issues with it, the three issues I see are that (A) it just kills people, which is something that the fighter can already do fairly reliably to lower-level people within reach, (B) it does nothing against higher-level opponents, and (C) if given to a boss NPC who's usually 2-4 levels above the party it can be too strong.
So here's a possible rewrite:
Tactical Strike: Spend all your Expertise dice as part of an attack to impose a condition from the following list on an enemy you hit: blinded, deafened, stunned, [rest of possible conditions]. Roll all of the dice spent, and the highest result gives the duration of the effect in rounds.
If the target is above your level, they get a saving throw to halve the duration and take a partial effect: [list of lesser effects, like stunned to slowed etc.]
If the target is four or more levels lower than you, you may affect one opponent per expertise die spent, you do not need to make an attack roll, and you may also apply the following conditions: paralyzed, unconscious, dying, [rest of possible conditions], which last until healed.
So a 10th level fighter can automatically KO up to 3 enemies of 6th-level or lower, apply any status effect desired to an enemy from 7th to 9th level with a successful attack, and can attempt to apply any status effect to an enemy 11th level or higher with a successful attack and a failed save. This seems like it would be appropriate for a fighter as soon as he gets multiple expertise dice, which is 5th in the playtest but could be as low as 3rd if we want to give the fighter more and better expertise dice as well.
I'd rather see a degree-of-success system rather than a number-on-die system, e.g. "If you beat their AC by 1 or more, you can deal extra damage, push, or trip. If you beat their AC by 4 or more, you can [inflict status condition]" and so forth. It's better than the proposed system because it gives the fighter more control because he can choose any valid option, and it makes him more effective against low-AC enemies rather than being at the mercy of the dice.