Here is what I found:
As of 24 hours ago, I switched from the AMD blockchain driver (AMD will not update this driver or support it, this driver will not work with more than 8 GPUs) to the latest AMD driver v. 18.3.1 and switched to compute mode. Here is what I observed:

Temp and fan control is now the same as Claymore. Ambient temp 22C, GPU temp 45-55C at 0-55% fan (my setting is -tt 55 -fanmin 45 -fanmax 70). This is on optimized BIOS settings (-cclock 1150 -cvddc 875 -mclock 2150-2200 -mvddc 850-900).
Everything seems to be running stable with the pool reporting avg effective 223MH/s.

My conclusion is: Dump the antiquated "blockchain" driver from AMD and install the latest 18.3.1 (do not forget to switch to compute if you are running dedicated mining rig, this has to be done to every card and restarted each time so grab a coffee. It figures AMD didn't include a way to apply this change to all the GPUs at once, that would be too logical)