People do indeed say that about sud rear discs, but also any car. As you noted it's not really correct either way. For front pads I have used Hawk HP Plus for vented 33 calipers and they are very good. I think the pad is common with E30 BMW and they have a one make race series in NZ where I understand the Hawk pad was/is the control, so supply is plentiful here. I have a slightly used set in the garage as it happens, but I guess it makes no sense to send to you.
Lonewolf I'm sure you're right about the adjusters. My recollection is from years ago in the pits at a circuit helping someone solve a rear brake (lack of) problem and when we removed the drum various pieces of the adjuster fell out onto the ground.
OP - it is unlikely to be the drum itself. Check for worn brake shoes, leaking wheel cylinders, incorrectly adjusted shoe to drum clearance, correct bias valve operation (both as suggested by Lonewolf) and if you can, get it on a brake dyno to try and narrow down the issue.