Agreed, I also run 2 servers that are pretty dang close to yours.
I have a bunch of 3/4TB reds too, and just made the switch to Seagate Archive drives. Haven't got them yet, still a bit worried about overall performance of them.
No issues here with the 8TB Archive drives. Half of them have been in service for 6 months. They perform just as well as the Red's (with writes being just a tad slower). I use my servers for media storage so the slower write speeds are not an issue. I do wonder about longevity, but only time will tell. I figure, by the time these guys start degrading, I will have upgraded to bigger/faster drives. In fact, I am looking forward to getting my hands on a Seagate ST8000VN0002 once they drop down to a more reasonable price.