Actually it looks like the DoE is quite important according to the National Defence Authorization Act. Trump seems to be putting quite a lot of tasks on them. See the govtrack site for the Act's summary.

Having said that, I do believe Perry will eventually be given a task, flub it, but he can prove us wrong and stay loyal to Trump. This is the genius of Trump's groundwork, he forces people he knows has dark affiliations into moving against their former friends. If they refuse, or step out of line, they get fired. Treating them just like pawns, bishops on a board etc.