Tomb Kings player here...
My tomb scorpion always gets shot by bolt throwers, which work fairly well against it (although I can generally use this to my advantage because my other units are not being bolted). 235 points for a vanilla steggie is kinda overdoing it used purely to fight an 85 point scorpion, though.
Otherwise his weaknesses are high strength attacks or poisoned attacks because of his high toughness. And for Sotek's sake keep your heroes away from him, killing blow + poisoned attacks make him very kill-y!