I've already run into an issue with the cross realms zones, and I didn't even have my bot at the time. I found, that while questing, it was much harder to do certain quests because the zones were running rampant with other people of the same level range. Quest objectives were very sparse, and they don't respawn very quickly, so it took me more than twice as long than it normally would to do certain quests.
I did notice that it either takes less exp, or you get more exp, at the level 80-85 range. I gained 2.5 levels from doing just a small handfull of dungeons and dungeon quests. The final bosses were giving me about 175k or more exp for a kill. This was without heirlooms and my guild was only level 19 at the time, so I'm not sure if I had the guild exp perk. I don't really pay attention to that sort of thing.
But, yes, I think this cross realm zones thing is going to be more trouble than it's worth when the bot's up and running fully. I don't see it being a good thing at all.