I would look at replacing the board. The system won't let us reflash it, power drain and NVRAM clear failed, which would only leave the board replacement at this time. You should be able to get along without the iDRAC, but reboots will take longer and fans are going to run at 100%, because the iDRAC is also the fan controller.
So think I bricked my iDRAC card. Was going through updates, starting with getting the BIOS to 6.6. Then Started in on iDRAC, going from 1.3 (I believe) and going to 1.85, which failed from the OS (Server 2012 R2) noting something about failing a secure copy. Seen something on these forums about getting the firmimg.d6 and updating via web portal. So I did that and after a long wait the fans suddenly ramped up like it was rebooting and the fans just never went down. About 20 minutes later, which might not have been long enough to wait, I rebooted the server from the OS. When it comes back up it says "System Services disabled," or something of the sort the F2 option, in the upper right and after getting the NICs and PERC up it hangs on "initializing the Remote Access Card." Tried clearing the NVRAM via jumper, no change. Time to buy a new iDRAC card?  Thanks
PowerEdge R710 iDRAC6