I think the current crop of plus tyres are as tough (or flimsy) as their slimmer equivalents. Most of the tyre manufacturers have caught on to this now. People were putting holes in tyres long before plus was a thing, so it won’t be going away.
I think the issue is more that if you run plus tyres at the sweet spot between traction and comfort, the combination of relatively low pressure and high air volume means they work like a high volume suspension chamber and effectively blow through their ‘travel’ without the ramping up you get with lower volume tyres.
So yes, the carcass may be the same as smaller volume tyres, but it has a harder time of it. You can run more pressure to counteract this, but then you end up losing some of the, erm, pluses of plus. That could be utter rubbish of course, but it’s how it seems to work for me.
The only tyre that’s survived long term in the Peak for me is the Ranger Tough 2.8, though the Rekon + was better than the lighter WTB casings and Schwalbe’s NN and Rocket Rons. The downside is that it’s heavy as a heavy thing and doesn’t use particularly grippy rubber.
One day I’ll finally get round to fitting Pro Core at the rear, though I’m not entirely sure which tyre I’d stick it in, the Rocket Ron maybe,