but it seemed like every time there was interference on Homura's part, the situation only became worse.

In the first timeline Mami and Madoka alone were able to defeat Walpurgis Night. Yeah, both died, but they won.
All five together, Walpurgis doesnt stand a chance.

It depends only of madoka and mami, because walpurgis seems inmune to physical damage. Unless kyoko and sakaya used an absurd amount of energy they wont be able to do much, and while homura would be extremely helpful with her time stop, she has always been unable to damage walpurgis.

IMO the sum of mami's and madoka's power is what can destroy walpurgis (assuming a no empowered madoka, form time line 2 and on she can destroy wallpurgis)

They lose.