Did you benchmark Prime 95 at stock?
The lower than desired no-volt change overclock might just mean your X4 965 was close to being binned as a 955. Not all chips in the same batch will perform equally.
30C ambient temps starting out is going to have some effect. Prime 95 and 67C is not too bad for a max effort on a hot day.
Usually you're thinking 22-23C for ambient temps. If you get something like 62C on a cooler day it's probably safe for long term too. I've seen the X4 965 max temps listed as 62C or 65C