What ISE version are you on now? I have just recently been working on a 3.0 customer whose timezone is subject to daylight savings and I have not noticed any issues before or after the daylight savings kicked in.
The topic of what timezone to configure is not well understood or documented. I have seen deployments running UTC on all nodes, or a mix and match of UTC and local timezone. All manner of combinations. I think it's all a misnomer. My theory is that the timestamp of the MnT is applied and that is used as the final timestamp that can be used in the Live Logs and Reports. The timezone on PANs and PSNs and PxGrid should (in theory) be irrelevant to what we eventually see in the live logs. I think that having the timezone set correctly for each node makes sense since it helps when troubleshooting an issue on a particular node - then the local logs will make sense.
You can change the timezone of a node without killing ISE. I have done that a few times too. It will restart services though
