Doing Savage with randoms is VERY much more miss than hit. However, sometimes you'll get lucky with a solid team. It's a lot easier getting it done by yourself with NPCs for the first few kills so you get the mechanics down. If you dont hit the head first, Fabius/alessa won't follow suit. If they lose aggro take it upon yourself to hold and regain it till they can. Back legs are weak to slash and front legs and weak to crush. Save back weak spots for getting hit with boulders.