And if you think the U.S. Attorney General has any business getting involved in House proceedings then you really have no idea what you're talking about.
Read up on William Barr's history and the legal philosophy that drives him, and you'll understand why: (1) he's the perfect man for the job he's in right now, (2) he will have no involvement in this House circus, and (3) the Democrats fear him more than any other Trump cabinet member.
At a time like this it's best to educate ourselves and stop thinking this is a WWE match.
You are unwittingly, IMHO, making an error which is understandable. You are still reasoning like the old rules apply, which they no longer do. You think the battle is in rooms with wood paneled walls filled with men in suits. The actual battle so far is a PR battle. If Barr were to arrest Comey Impeachment would be a side show. What is on TV screens right now would be Rat corruption and crime not a kangaroo trial which is currently on Prime Time.