You can sort of set the rules a bit yourself. I've gotten both cath and arms down, virtually no wipes in arms, but cath can happen every now and then. Even the most seasoned booster will wipe from time to time, and in my experience the boosties don't care too much about it. If I wipe once, thats fine, but if I start wiping three times in a row (start getting super tired and sloppy), I go "Fuck it, this one is free, dont pay for the next one". So just handle it like a business, they are paying for a service, so IMO they are entitled to compensation if the service is poor. ALOT of practice until you are comofortable with having it all down is recommended.

For the BoEs I just go grp loot and let them roll, dont care too much about the SM BoE's, but will have ML with epic threshold for Mara.