WTB frequencies are tough as old boots- mine (29er, i23s) have taken highland water bars, alpine rocks and the rockier bits of bike park wales and antur among others in their stride with no problems. A friend managed to roll the tyre off on one of the particularly slaty bits of antur and stopped on the rim, so they’ll survive that too.
To be honest if I was planning on being anything less than wantonly abusive I’d probably take the KOMs- peak district riding they’d probably be my choice as you can ‘size up’ on width for the same weight.
Or you could do what I’m planning on doing for my OH, also on a mach 5.7- she trashed a rear wheel so I rebuilt with a frequency i23 rim, if I do the front I’ll use a KOM for the extra width and slightly less weight.