Easter Egg hill has a by pass, I didn't even realize it until last year when I was on it and someone pointed it out. That said if I can spot a Liberty with only a 3" lift down it, a Rubi will have no issue. Just stay off the top falls on the optional chute.
A better question would of been what trails not to take a Stock Rubi on because they are capable enough to do practically all of them, that are at least in the Charles Wells Guide. Stay off of Pritchet Canyon, Moab Rim, maybe Kanes Creek if it got tore up over the last few storms (generally does the month of Sept).
An even more important question would be what trails do their driving skills warrant? Fun newer trails would be Metal Masher (by pass Widowmaker), Seven Mile Rim, Gold Bar, Dome Plateau, Top of the World, Elephant Hill to name a few. One of my favorites still to this day is Klondike Bluff to Tower Arch, to Eye of the Whale. You end up ending at Balancing Rock in Arches