Unless something has changed with his boat rigging, I believe Mark is only running divers, no riggers, so that would explain the heavier leaders. I think it's more important on riggers to run a lighter leader. I run 50 lb big game leaders on my divers and don't generally lighten that up when I put a spoon on a diver instead of a flasher/fly. I was initially worried about the heavy leader killing the spoon action but have had no trouble catching fish on spoons off the divers, so maybe it isn't as much of an issue on dipsys.
Tim