Definitely worth doing the Corpse Road but Mosedale is a boggy mess so avoid that. Instead, from the top of Gatesgarth make a 90 degree turn and go over Branstree, Pillar and Selside Pike and that drops you pretty much onto the start of the Old Corpse Road descent.
The Old Corpse Road was entirely dry a week ago and it hasn’t rained since so will be in fine fettle. It’s not the usual Lakes Tech fest but it is a lovely flowing singletrack descent with stunning views and beats Gatesgarth any day.
My favourite variation as I live near Haweswater is:Haweswater-Gatesgarth-Harter-Nan Bield-Staveley (scoff)-Gatesgarth-Branstree-Pillar-Selside Pike-Old Corpse Road-Haweswater Lakeshore. A bit of footpath action there so some discretion required.
Makes for a decent length of day with the extra bits thrown in. Did I mention not to bother with Mosedale?