I have not had any trouble at all with cooling. I have ~81 C on the Hotspot with 1.0 on the voltage and 80% fans. Remember that this GPU is designed to hit 110+ C before it throttles, unlike most recent gen GPUs that will throttle around 83-84 C by default.
That's interesting. At least on my cards (AMD 50th anniversary & AsRock cards) around or above 83 C (as reported by MSI Afterburner) I start seeing diminished Ethereum hashrates. I believe this is a core limited card, so any core throttling will immediately impact hash rates.
I have a 50th anniversay R7 hashing occasionally here, and it's very reliable around 90.7 Mh/s. MSI Afterburner says 74 C, Fan speed set at 64 %, Core 1801 MHz @ 980 mV, Memory 1040 MHz, Power limit -10%
https://eth.nanopool.org/account/0xa63ffc523e284bfb4a09b46ed2336afe824c57eb