I think technically you're being wasteful of time expenditure for everything but reaper points if you do not run on r1.
However I prefer challenge to pure XP so I play mostly Elite at -1, -2 levels, meaning +3 to 4 levels on the quest. That gives me the best bang for the buck in terms of difficulty vs progression. R1 doesn't do that for the builds I play because the mana drops keep me from having to shrine or make decisions on buff recasts when I am disjuncted. When I play a melee-based non caster I run r1 instead.