Revan and Nihilus. None of the One Sith have the knowledge required to resist Nihilus' drain, as his drain is unique and requires very specific circumstances or knowledge to defend against; so in that regard Nihilus pretty much has an easy win. SoR Revan is above any of the One Sith anyway, save for Krayt Reborn who I see as around the same level as Revan. Old Republic team wins.
Nihilus can take Talon and Maladi at once. He is probably way beneath them as actual combatant, but his inhuman Force power, the fact he can draw on his Drain spontaneously as a part of his nature, makes it impossible for the two to succeed in a fight. Sooner or later they fall, as Nihilus's hole being composes of "the Drain personification" he can use instantly. Either he does that quickly, or when surrounded and wounded.
Revan vs. Krayt, Wyyrlok and Nihl is a good fight. Krayt wouldn't hold his own 1v1, but Wyyrlok provides good backup. Nihl, though, is pretty much nonfactor. He is fodder compared to people like Satele or Marr, who could kill him instantly any time they wanted (given Marr's parity to Malgus and superiority to people like Thanaton or Baras), and Revan could ragdoll them mid-fight along with absurdly high bunch of other people.
Still, Revan is far more powerful than either Wyyrlok or Krayt, and holds power literally beyond their ability to comprehend. Combatively, though, Revan would win easily against Krayt, and stomp Wyyrlok 1v1, but together the two are pretty close to Revan in sheer lightsaber combat. It obviously holds more importance than direct Force attacks, which rarely decide the fight (unless we're talking about huge disparity or both sides being in the top tier)during a heated lightsaber combat. Especially, of course, when you consider how fast Force users are and how difficult it is to find a momentary opening and timing for more extensive Force usage. So, with that, I think they truly press Revan until he eliminates Nihl, and some time after, but in the end they could never hope for a single scratch on Revan.
Team 1 10/10.