Hey mate. Well, it's an interesting question actually. The only thing I have succeed with a 100% is RAF Grinding. I ran Grind / Instance on Bot A and Partybot on Bot B. I experienced alot of trouble AFK'ing this setup, since Bot B would'nt leave instances after it was done, and sometimes one bot left the other which cause even more problems, since Bot B would just stand there in the dungeon/grind zone trying to figure out where Bot A was. Also it happened more often, that Bot A did'nt invite Bot B to his group after instancing. So I tried something else. What about putting BOTH bots on Grind / Instance (NO partybot). And it actually ran very smooth, much better than before. Now Bot B does'nt follow Bot A, but the actual leader of the group, which i also see as a plus. The only thing wrong with this setup, is that now none of the bots will invite the other, which means you have to monitor it at all times while playing, so you can manually /invite.
You also talk about Questing which I find even more interesting. Cause after my failure with Grinding and doing Instances, i thought to myself, what can I do to make this a succes. I tried out Questing. What there is to mention here, is that your bots will not Quest together, just next to eachother. They will not neccesarily be on the same quest at the same time, but will at some points "overlap" eachother, and therefore gain the RAF bonus exp from killing mobs. What I did to twist it for max exp, was i put BOTH bots on Questing / Instance, and I think this is the way to go. Questing is massive exp gain right there + mixing with instances you can't possibly be getting more exp by farming mobs, even though you get RAF bonus. Another bonus is you will be mixing items from quests and dungeons too, so you will find it very hard to be undergeared. Notice: to run this setup, you will still have to monitor your bots VERY MUCH, since you will have to manually /invite after each dungeon.
So my conclusion is, that you can level insanely fast with the use of RAF, but only if you are willing to monitor your machine. I have not yet tried fully RAF Grind 1-85 but I can't imagine that it will be faster than Questing solo, so RAF won't be 100% AFK'able untill the Partybot is fixed, or they find a way to make them actually quest together, doing the same quests and assisting eachother. Now, IF you find a way to do any of the above things i told you werent possible, please notify me, as I find it very interesting to exploit new ways to faster gain.