first, don't let what he says affect you too severely.

Secondly, stoneskin is situational - there are some fights thar make it vety useful (slow hitting or light hitting bosses) but not some others. i rrmember stoneskin being very useful when fighting Garuda SM, Idgebind, and the Darkhold bosses etc. but if the mobs just hit too damn hard at times, it may not be worth it to use stoneskin because you dont want yhe tank to hover at around 25% hp.