I have been quite worried about the bumpmaster variant of this list as a Palp-aces player, and finally got to play against it the other day. I wasn't all that impressed with it to be honest. I was largely able to avoid the bumpmaster for two consecutive games, and I found that I now only need to account for two arcs.
In the first game, I was running Echo, Omega Leader and a Yorr/Palpatine shuttle. It was quite easy to avoid the bumpmaster with Echo, and I didn't allow a single torpedo to be fired all game(there was an opportunity to fire a proton torp at OL, but my opponent opted not to because of OL's ability). We discussed it afterward and he still would make that decision, but I would not. The only way to get damage through on OL is through focus fire or throwing lots of dice and hoping for a good roll. Edit: or by using the bumpmaster!
In the second game, my opponent wanted to play against the new standard Palp-aces list: Palp shuttle, OL, Inquisitor, and Wampa. This one was much closer, but I still managed to avoid the bumpmaster for the first half of the game. He eventually got OL a few times to kill it, but by this time I had already erased the proton torp carrier and was one hull away from erasing the plasma carrier (both plasmas were fired this game, but no protons I believe). The Inquisitor had an easy clean up job on the bumpmaster.
I am definitely more worried about the standard triple torpedo U-Boats than the bumpmaster variant as an imperial player. I know others disagree with me, but I feel more threatened by the extra torpedoes.
I'm curious what sort of approach and asteroid setup you used. Did you try to leave things fairly open or make a cluster in the center they had to go around?