Yup. The killer on these things is usually actually feedback phase shift. Sometimes the output load can have a complex reactance which turns the supply into a c

Yup. The killer on these things is usually actually feedback phase shift. Sometimes the output load can have a complex reactance which turns the supply into a convenient power amplified oscillator. Fat output capacitor solves most of these problems but sometimes that has its own problems (old HP supplies had nice barrier strips so you can deal with them yourself :). Obvious trade off is step response there etc but your load should be properly decoupled anyway. Lots of problems on power dissipation there as well as you state. The HP/Agilent designs tend to use an SCR pre-regulator which reduces Pd on the pass transistor considerably. But of course the principal cost in these things now is shipping and profit margin so it works out cheaper to cost cut even more and shift a small heatsink with a loud ass fan on it that does your ears in. Grr. (this is one of my many reasons for disliking Keysight) The old HP designs are very robust. I've owned a few. Almost impossible to blow up, even the big ones. I actually had a Harrison one built in 1967 that was still working unrepaired and unmodified until I sold it recently. Bob Pease did an interesting "zero output capacitance" supply article a couple of decades back. That was surprisingly stable.