You can't brick your card from underclocking the memory too much.
DOA means Dead On Arrival or Defective On Arrival. Can't be DOA if you got it out of the box brand new and it's working
lol. I was thinking the exact same things.
At worst a driver could get corrupted as the entire system freezes when you downclock the memory too much. The card can't die from any amount of downclocking, hell, even excessive undervolting will just freeze the system.
Screen artifacting after changing clock frequencies doesn't indicate bricked memory or a broken card, that happens every time when components are run at specifications not suited for operation, which means you have to tweak them
& A DVD drive can't be dead on arrival if you have been using it...