That's not been my experience - I run this in a Synology with a WD Red (WD60EFRX), Ironwolf (ST8000VN004), and a Hitachi (HDN70280ALE604) All are at the 39C mark while the array is repairing itself (ie at load). This is only Day 2, mind you.
Edit - now that the array has repaired itself here are the idle temps:
- Ironwolf - 37 degrees
- WD Red - 34 degrees
- HGST - 36
- WD EDAZ - 38
So hotter, yes - but not blazing...