Yes, with mental shield, without any derangement attack boosting effects the chance to land is small.
Chance to land on mental shield can be significantly increased with derangement attack boosting effects from: Earrings of Zaken, Earring of Antharas, Jewelry augments, Aden earring, olympiad earring, ring of beleth.
On the other hand, there is no other way to increase the derangement resist of summon than Mental shield.