I have a mix of R510, R610, and R710. All seem to have the connection failures. My Vsz is on version 220.127.116.11.227. I started having the connection failure problem on the first version of 3.6. My APs are on firmware version 18.104.22.168.354. I can downgrade the APs to the latest 3.5 version and the connection failures go away.
5ghz channel width is set to 80MHz.
On the non-DFS question. I have the channelization set to Auto. Out of 110 APs, i have 14 on channel 36 and 9 on channel 149
Running 22.214.171.124.227 as well, with all APs (72 R610, 2 T301s) on 126.96.36.199.354. No problems other than the incorrect connection failures, which has been mentioned here. 5GHz channel width is set to 40MHz. Currently 13 of the 74 have chosen a non-DFS channel.