We can't accurately judge dark side Yoda. Dookus claim that Yoda is stronger than Sidious is held back by. The fact that Sidious never showed Dooku his full power as far as we know. And being strong in the dark side also requires having training in techniques. Yoda turning to the dark side doesn't necessarily mean an OP power boost.
Anyway, I think Mace might be able to Vaapad their darkness back at them. Yoda's support just makes it worse.
''In a flash Dooku saw how foolish he had been, trying to urge the old Master to the dark side. If Yoda ever turned that way, Sidious himself would be annihilated. The universe had yet to comprehend the kind of evil that a Jedi Knight of nearly nine hundred years could wield.''
Dooku isn't an idiot. I think he is well aware of how powerful Sidious is.
I think DS Yoda can solo this gauntlet honestly. From the sounds of it he could curbstomp Sidious. Also I interpreted that as more narrative than just Dooku's speculating.
''In a flash Dooku saw how foolish he had been, trying to urge the old Master to the dark side. If Yoda ever turned that way, Sidious himself would be annihilated. The universe had yet to comprehend the kind of evil that a Jedi Knight of nearly nine hundred years could wield.''
When Dooku immerses himself in the force, he is able to, very accurately at time, sense a force-user's power on a metaphysical level: "Powered by the dark side, Dooku's perception took the measure of those below him with exhilarating precision."
...So it seem logical to assume that he could have roughly gauged Palpatine's power as well-- enough to state that he was "beyond power", at least.
Thus when Dooku took note of the power a dark-side-embracing Yoda would have: "It was Yoda as he might have been, or could yet become: a Yoda gone rotten, a Yoda whose awesome powers had been utterly unleashed by his connection to the dark side. In a flash Dooku saw how foolish he had been, trying to urge the old Master to the dark side. If Yoda ever turned that way, Sidious himself would be annihilated. The universe had yet to comprehend the kind of evil that a Jedi Knight of nearly nine hundred years could wield."
...He likely wasn't hyperbolizing in a self-monologue. Just my opinion.
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At any rate, if we take Dooku's claim at face value(as was likely what the thread starter had in mind), then Yoda gets to #8 for sure, and possibly clears(I have no idea what Prime Luke is capable of.)