The Sound four utilizing Stage 2 Curse Mark was left winded fighting two Jonin who were themselves returning from a mission and not in the best shape.
To be fair, using the Juuin V2 was a precaution since they knew it was Jounin they're facing, in addition to being in a hurry. They defeated them without suffering any injuries in return.
What's more, powerscaling's not that dull in Naruto, at least in part one. Knowledge & matchup play huge roles. Counter example would be Kidoumaru alone decapitating 2 Anbu (which are > Jounin) with his webs. He also would've defeated the entire rescue team (bar Naruto with Kyuubi powerup) on his own if Neji hadn't been the perfect counter to his hax. 'Nother example is Konohamaru beating Jigokudou Pain who prior to that bested 2 Jounin.
That being said, they still lose to the Hokage by a landslide, even the Kage's weak versions massively outclass the five in every aspect, not to mention Mokuton + Hiraishin hax.