I dunno ...
Tieflings, maybe i get that wrong, but i believe that they were runaways from that city that ... i dunno right word, fall(?) down to Avernus ... or from some other city, and people chased them out since that city fall(?) down to Avernus, and they were affraid that it will hapen to them aswell ... but i dont recall any word about them being litteraly runaways from hells. O_o
Druids seem quite regular to me ... yes, their acting leader was power hungry, corrupted and kinda mad ... but the others?
Wat is odd about Githyanki with a dragon? I mean it, i dont know.

But as i understanded that, the only thing that is odd about them, would be its just a small group, since when Vlaakith sends her troops in material realm, its usualy whole army for raid.
Same story ...
What is odd about goblins raiding towns (note that this "town" consisted of 4 buildings

).
And about Drows raiding other town? O_o