Finally found something that was more than a resistor out of value. I swear I verified the two test points around the AGC/AFC tube but on checking again I appear to of been wrong.
(probe ground was chassis during testing)
Both waveforms are nowhere near what they should be and are oscillating. Well we have already replaced all the resistors around this tube and the tube itself was checked again for good health and swapped for the 6U8A that was being used for sync sep./ noise limiter with no changes being observed. All I can assume at this point is that a ceramic or mica capacitor has failed somewhere close and it's wreaking havoc. Does this sound correct?
Edited: I missed the noise limiter/sync separator circuit as well. Both of its waveforms are also not correct and there is glytchyness on the test point for the 12BY7 but everything else is either spot-on or close enough.