The team takes it (narrowly).
Let's just assume, as a Vader-tier combatant, the Hero of Tython skirted the top of what Gillard calls the 8s (by the time of SoR).
Still wouldn't have been strong enough to stand a chance against Darth Nox and the Wrath together.
Arcann may have had a clear edge over the Hero in Chapter VIII: Taking Flight, but the Hero only had HK-55's (admittedly useful) help.
Still not as useful as another high-tier Force-wielder.
And as soon as Koth stepped in, the tides were turned.
Originally posted by Geistalt
'Cause face it: Arcann's not > Vader.
A. this for Act III of the original storyline, a good three years before KotFE even begins.
and
B. Arcann still ragdolls these people after that point, so even if it was for Chapter VIII of KotFE, they'd still lose.
That's not even getting into the retardation of the HoT being even remotely Vader level.