Eh, Mark and Elena were the least involved in the bullying of Jess and Cody out of everyone. Elena basically stood there and just watched it happen (which is being a prettttttty bad friend and arguably just as bad as being involved) but Mark tried to help Jess and Cody out a little, and he got ostracized by the Paul cult for it. You're pretty right on the rest of the Elena stuff though, lol. I will say tho that I would've preferred Mark and Elena over Josh and Paul because I can't stand Paul, but I'm not exactly mad that neither team made it on the cast.
As for Kym and Alli, if it was a full-fledged all-star season, I'm sure they would've made it. For ratings purposes, I think casting went with four of the best teams that they could have...and then they threw in Art and JJ to try to make drama with Rachel. Aside from that, I wish they had a more even show split where it was like a 4-4-3 split between teams representing each reality show rather than 5-3-3. I would've taken another survivor or big brother team instead of Art & JJ.