With Regards to Slashing Debuffs, Raid Compositions, and Tank Parity.

[Reynhart]

That's an incredibly well written plea, my good fellow.

There's just a little problem when comparing all the three debuffs (that you partially acknowledged). Nowadays, both NIN and WAR can put up a slashing debuff. But the combo used to put slashing debuff is the weaker one for the NIN.
WAR, on the other hand, needs to put Maim for their own good, so they'll do the Eye combo in their optimal rotation. Thus, if you have both, let WAR put the slashing debuff and NIN can rotate between its other combos.

For piercing, you adressed that by switching Disembowel and Phlebotomize. First, yes, it would be strange to put two DoTs in the same combo, but even stranger to have acces to a piercing debuff outside any combo. If we suppose that Disembowel stay in place, it means that DRG will do Disembowel in their optimal rotation so it's less useful for PLD to have it. Especially since, if you off-tank, you'll rarely use RoH.

For MNK, it can work since DK is less powerful than bootshine if you can hit from the rear.

But, it'd still be strange to have debuffs that don't even increase your own damage. Meaning that if you don't have a MNK, the blunt debuff from DRK isn't doing anything. And the same would be true for a piercing debuff if you don't have a piercing DPS in your party (Less likely thant MNK, yes, but not impossible).