I'm currently mining with 2 GPU's. My XFX RX580 8GB sits at 90c while my R9 280x sits at only 74c.
Both are running stock. Mining ETH with 280X I get about 13.3 mh/s and with RX580 I get 22 mh/s.
Thats way too hot! Use this example to get them lower with TPD:
http://mylifegadgets.com/setup-ethmonitoring-miner-software/I have running 580x at 58C