Correct. It is immune to counterattacks. It has some other bugs (I think)

ie. it VERY often hits with critical strikes while not having any special ability in that direction (unless we treat lighting attack as critical).

the other bug is that it overuse the titan breath spell. 

It uses it probably whenever possible, even when facing pronesafe enemies (mounted), even when it gives it no tactical advantage (because the enemies are faster, and without backing up shrills to use the prone advantage).

on a side note, the spell is fairly useless without damage, I don't think I ever used it when having the elemental summonned or when having the prerequisite school of magic. It could for example give each opposing caster a -10 to spell mastery per cast if we don't want to give it damage