They could always go for a twofer. Souleater combo is still for MP, add a 2nd GCD combo (that does the same damage as the Souleater combo) for Darkside generation. Edge/Flood still need MP to be used (albeit probably with a cooldown attached), Blood moves drain Darkside, necessitating alternating between the two combos to keep your resources up while preventing it from being too hectic due to the longer time between Edge/Flood uses. This of course, would require a fine line and I'm not sure the dev team could pull it off tbh.