I'm sure I'll get called out on this... Normally any god (god-like being, etc) can be permanently slain if he/she is killed on their home plane (plane of origin). Not the case in ToEE.
Why would a god need anything? No god is all-powerful, all-knowing, blah,blah, blah... They are just powerful supernatural beings. They would be trippable, killable, etc for the usual reasons. None of these guys are even powerful enough to run a country without help. Keep in mind when you 'kill' Iuz, it's just an avatar. He'll be back.
Gods don't need anything except an orb of golden death and One Ring to rule them all, One Ring to find them, One Ring to bring them all and in the darkness bind them.
It's a combination of both. The tripping and Scather is an exploit. The "cannot initiate dialogue while tripped" is a glitch. From what I've seen around the boards, people didn't really kill Iuz in the 2-3 turns before he's supposed to be taken away by Cuthbert. Feel free to correct me though.
I've seen screenshots of dead Cuthbert on this board, feel free to search for it. IIRC, he's got a pair of boots.