FWIW, I've been having a lot of trouble with my MBPr-13 and iPhone 6 recently. With either device, I will be connected to WiFi with a good signal, but suddenly unable to ping anything on the network. I can solve the problem immediately by disassociating and reassociating.
I have yet to find anything meaningful in the logs, traces, show commands, etc. No ARM events or anything else I've been able to correlate. My next step will be to check the dataplane sessions, but I haven't yet been within convenient reach of a wired computer to troubleshoot. Most of the time I just grumble under my breath, reconnect, and go on about my business.
In my case, firmware is ArubaOS 6.4.2.9 with 2x AP105. MBP is using the same Broadcom BCM43xx.
At work, I switched to using an Aerohive AP in my lab for comparison sake, and in the last couple months, I've had zero issues with the same MBP, same iPhone, and also my work iPhone 5S. This leads me to believe the problem is either with the AP105 firmware, ArubaOS, or some interaction between them and the Apple drivers. Troubleshooting is slow-going, as I focus on one change at a time, and only then when I'm feeling motivated enough to stop what I was doing to dig into it.
Probably not very helpful, but I did find it interesting that I'm having a similar problem, with the same chipset, and within one minor version of you.