Oh yay, so it seems like I sort of had the right idea! I'll definitely stick to Diurnal with a SCH co-healer like I've always done, but I might experiment a bit more with regen stacking with a WHM as I go along, or at least use it on lower level stuff if only so I have more time to DPS and spend less time reapplying shields when they break.

Thanks everyone for your replies!