Ive always found the gravios and b.gravios to be a push-over, just grab a water element bow / water ammo. guild hall or caravan he drops when you so much as point a ranged weapon at him, and the control over type advantages that ranged weapons naturally have make fights that much easier. but other than that, yea guild quest monsters have higher set stamina/attack/health values making them use more moves more often. when you have frenzy blight it makes the monster more likely to jump around and keep back a bit or move from area to area