Ahh. My thing is I never could rationalize Twilight Sniper. It seemed to me like one of those things where Twilight was considered worst pone so the two genius classes were given to others based on stereotypes, so she sort of fell in the leftovers using weaponized math as an excuse.
Even their personalities aren't that similar. Given the Sniper doesn't have a lot of exposure, I think people heard the words 'Be Efficient' and just clinged to them and made excuses.
I personally like Fluttershy as Sniper and Twilight as Medic. Sniper has lots of animal and nature themes and does well to avoid the actual combat, and Medic is a thought class that requires attention to detail, whose powerful ubercharges allow him to lead pushes and he is basically the first one anyone wants to kill. Also, he seems thrilled at the idea of learning actual magic.