I've got a 300tdi with heavy duty standard procomp on but it keeps eating prop donuts would I be better off putting a 200 prop on ?.......

Yes although even then it won't be an ideal angle. But with a UJ you will be far better off than the donut which isn't designed to take much of a change in angle . You'll need a 4 bolt flange as well as the 200 prop.
If you have a lift then really you should have cranked trailing arms, caster correction radius arms etc and if you believe they work, a wide angle prop. But all they do is allow more movement before maxing out the UJ's full spread. It won't avoid them getting worn so just grease your UJs, fit GKN and keep an eye on them.

Thanks will get it sorted