He always struck me as the calmest, most unruffled member of the team. Nothing seemed to really get to him, no matter how dire the situation, he just dealt with it. I don't know where the idea that he's some sort of defenceless woobie comes from, he's not the woobie type really. (Not that I don't occasionally enjoy a bit of woobie Ianto, just most of the time he's anything but!)