I find it is often best to kep it as simple as possible when trying to RMA a drive. Tell them you want to RMA the drive, when they ask whats wrong with it you give them basic symptoms, like it clicks alot and won't boot or won't spin up... etc.
Basically be stupid and answer the questions as minimally as possible, never elaborate. Never tell them they were RAID or anything fancy, they were just in the computer as normal drives. If they give you any crap, ask them if they are refusing to honor thier warranty. When they try to blame it on you in any way or any other crap, just say, the drive is has failed and it is within the warranty period, are you refusing the warranty? This is your mantra, thay HAVE to honor their warranty as long as they cannot prove you caused the failure. That is the law.
Remember you don't have to give them any info on how the drive was used, it is up to them to prove you misused it. Do not give them any reason to deny you before they even recieve the drive.
I have used both Maxtor and Quantum. I like them both. I have had failures from every drive brand manufactured, they all have duds. My most resent failure was a Maxtor, and I would by from them again, and probably the same model.
PS Maxtor has a lovely online RMA program online, I got the # online then sent the drive and had a replacement within 7 working days. They do NOT repair your drive, they send you a refurb(but then doesn't everybody). Haven't rma'd a Quantum in about a year, so can't tell you how they deal with it these days.