Where to start...
I'm well aware of the different versions of Super Buu, but your memory is definitely betraying you.
Base Super Buu (Good Buu + Pure Evil Buu) was the version that fought SSj 3 Gotenks and was roughly equal with him. This same version of Super Buu tried fighting Mystic Gohan and was dominated, so he decided to make a tactile retreat knowing that he couldn't beat Gohan in that form.
Base Super Buu returned just in time for Goten and Trunks to be able to fuse again and baited them into doing so. Once they became SSj 3 Gotenks, Base Super Buu absorbed Gotenks and Piccolo at the same time becoming Gotenks Buu or Super Buu 2. In that form, Buu was able to use Gotenks added power and Piccolo's tactics to beat Gohan pretty easily; however, his cockiness got the best of him, and Buu allowed the Gotenks fusion to wear off reverting to Piccolo Buu or Super Buu 1.5. In this state, he was weak enough for Gohan to beat, so he had to come up with another plan on the fly and manged to absorb Gohan becoming Gohan Buu or Super Buu 3.
Gohan Buu was the version that easily beat Goku and Vegeta before they were able to become Vegito. Vegito easily beat down Gohan Buu, but allowed himself to be absorbed in order to free Goten, Trunks, Gohan, and Piccolo turning Gohan Buu into Base Super Buu or Super Buu 1. The scan I posted earlier was after Goku and Vegeta removed those four from Super Buu (that's the drop in power that Goku was referring to in that scan). Despite that drop in power, Goku still didn't think that he and Vegeta stood a chance.