He would've died, plain and simple. He thought he could take all of them at the same time (If they stayed in base form than sure) but if they were all SSJ2, Dabura would've been insta-killed, Even if they all rushed him as SSJs than he'd still be insta-killed. Majin Buu probably might've woken up but Goku was sure he and Vegeta teaming up would be enough to beat Buu before Vegeta pissed him off when he fought him solo. So if that would've happen than this whole thing could've probably been over with within an hour give or take, maybe two.