Sophia IS one of the easiest EX Primal fight, maybe beaten only by Bismarck.
By comparison :
Ravana - expect a wipe people don't know how to deal with Swift liberation and Final liberation
Thordan - expect a wipe if people don't know how to deal with tether , don't know how to deal with Wildcharge etc.
Sephirot - expect to die to purple, green if people don't know how to position. On second phase if at least one orange guy dies then at least ONE green guy will die too, and god forbid if earthshaker target don't know where to run to, and if someone fell off then that's final.
Nidhogg - multiple dps check during the fight (adds, fang and claw), with some deadly mechanics during them too.
Sophia? Sophia has almost no mechanics that required co-operation except for the Sin&Punishment positions, and NO insta party wipe AT ALL. If someone died you can just revive them, over and over. DPS check is also very lenient (group with decent DPS can clear her in 8-9 minutes, enrage timer is 11 WHOLE MINUTES). Cintamani can be dealt with just Medica 2 + Medica (Or any 2 aoe heals, for that matter). Tank buster that can be survived in DPS stance (Holmgang, at least 2 times, Sentinel + Sheltron etc.)