I am surprised that they didn't do something like in the gameboy advance game, Super Sonic Warriors.
The alternate storylines in that game are awesome.
Anyways for Piccolo in Super Sonic Warriors after Majin Buu regenerating from a seriously powerful attack, Piccolo heads off to Planet Namek where he wishes the Evil King Piccolo (Piccolo's father) to be resurrected. Then Piccolo merges with the Evil King Piccolo and become the true Namekian Legendary Champion and fights Super Buu. Piccolo manages to seal Super Buu away with the Evil Containment Wave. However, Super Buu was eventually released thanks to Gotenks. However, with the strength of both SSJ3 Gotenks and the Legendary Namekian, Piccolo. Super Buu was finally destroyed.
But anyways back on topic. Humans are generally extremely weak beings in DBZ. The only exception was Uub.