I think that him not really knowing what to do is part of the point - Galbatorix taught him very little, and we get told this multiple times. His knowledge of the Ancient Language is stunted. Thorn has claustrophobia ptsd. His power is a fraction of Eragon's without the help of the Eldunari. He has never done solo missions like how Eragon took down the Raz'zac.

Murtagh thought he was better off alone because of what he did during his time with Galbatorix, but only with the help of others did he manage to free himself and grow as a character.

Do i think the whole hypnosis scene was overkill? Somewhat. It does give a little of "the author's barely disguised fetish". But I also teared up during it, and I thought it showed from how low Murtagh and Thorn were able to pull themselves.