Your squad members in general are so overpowered compared to similarly leveled players that the only thing that can really threaten them are persistent ground AoEs from bosses, and only the ones that they don't take reduced damage from. They can sit in Aiatar's poison pools or the electrified water from the biast in Halatali all day, but the AoEs from the final boss of both Halatali and Totorak can definitely KO them if you don't re position them with disengage.