Do I need a stronger wheel?

Sorry, not keen on presuming ignorance.

Basically if all of the bits and bobs on that axle, most importantly ending in the cone, are loose then the rear wheel will feel like hell. To check, grab the top of the wheel and see if it rocks back and forth in the frame. If it does, and it's been like that for a while, take it to a shop and have it serviced. I only ask because untrue wheels don't always feel bad and rarely "violent". Also check your tyre, if it's getting frayed this can add play to the ride.

If not, return to plan A

Have checked and there's no side-to-side play with the wheel bolted into the frame so I guess my cones are OK? Tires are only a few months old and in good condition all over.

People on here will advise Deep V's etc. But I'm not a fan of gaining stiffness through depth alone. Its not like you see many touring bikes designed for heavy loads, rocking H and Sons hipster rims.

I'd go with a strong eyeleted rim with 32/36 standard butted spokes (Sapim Race, DT competition, etc).

There's loads of touring rims around. Some examples.

Velocity dyad
Mavic A319
Mavic A719
Halo ExciteR
DT Swiis DK540

All the above rims are wider than a standard road rim, so will only be compatible with 25mm or larger tyres. But a 25mm tyre on a 24mm wide rim, will roll nicely, and will be less likely to pinch flat, then one on a narrower rim.

I have recently built some new commuter/load carrying wheels with the Halo ExciteR's and really liked them. They where really easy to build with, and the wheel feel nice and stiff, even when the bike is loaded.

Thanks for the suggestions. Those Halos do look pretty good.

If you mean the Mach 1 Omega rims, one of my bikes has had these, and I've ridden thousands of miles on them, with no problem at all. And I'm heavy (19 stone, or close enough), so I'm wondering what went wrong with your wheel.

Was it accident damage (deep pothole), carelessness (jumping down stairs as if on a big BMX), or was there maybe an underlying fault (wheel not built up / tensioned properly)? It just struck me as odd, that particular rim would collapse, as I've not been easy on mine, and they've lasted really well.

Yup. Those are the ones. I weigh about the same as you. I'm pretty paranoid about potholes and haven't hit any big ones and I'm certainly no trickster so I guess that leaves the possibility they weren't built up properly at the start. Will swing by the shop I got them from and get their opinion.