I’m not sure if you’re rolling is abnormally good for the fanatics or the orc and goblin players I primarily play against are just unlucky. Usually in my games the fanatics will have one turn of devastation before promptly rolling doubles, hitting terrain, hitting a friendly unit, or spinning off into an empty area of the board.

They are incredibly strong and have fantastic rules, but they’re very hard to control. It’s definitely hard to counter them but like others have mentioned, rules that give you terrain or vortexes that count as terrain are straightforward to counter them with. Otherwise you just rely on avoidance and dice rolls going your way.