She's very all-or-nothing. She's either taking no damage at all or dying instantly. Personally, when I used her, I found her to not be durable enough as well, but overall party level is going to make a significant difference. I don't know about you, but I generally tried to keep my team as low a level as possible while still exploring everything. But if somebody's grinding for bosses and reaching higher levels, especially if they're using, say, a draft team with lots of weaker characters, she probably ends up a much more potent character.
That, and as someone who was just trying her out to see how well she works, you've probably invested less skill points in her than someone who knows they're going all the way with her. She'll be lower level as well, etc. All of that matters more than you'd expect, since as I mentioned she's a character who needs to stay just above a certain threshold of invincibility. A bit to weak and she's suddenly crap.
