My Dynaco MkIV's have micro adjust bias pots also. They were tempermental with bias setting until I installed new tube sockets (teflon) and GEC KT77 re-issues in them. Now, once warm, they almost never need re-biasing.
I used to bias at 1.56VDC and would know when the bias had climbed to 1.62 when the highs hardened. I now set to 1.25VDC. That said, I did test different bias settings for sound and found only the higher setting to affect performance.