She has seemed fine on defense for me fwiw. However, I run a defense where everyone fires in 7 or less tiles, but I think that she complicates things for the attacker.
The hit isn’t the greatest, but depending on how often she fires, she can really nullify a lot on defense (beyond Telly, she stops blinds, def down, all DoT, att down, etc). If you’re attacking, you’re forced to just use your special for damage (a bad deal if you have JF or Vela with you) or wait her out for two turns if there’s no dispellers and then hope she doesn’t fire again.
She also takes your heal, so waiting her out and staying alive becomes an issue (the heal is a big deal; she gets almost 1300 on a BT heal if 5 are on the board).
If she’s in a fast defense that can pressure an attacker on a bad/mediocre board, I would argue she could excel because she can help force attackers to do things they don’t want to do, which I think is what a good defense does.
On attack, timed right, she completely nullifies Telluria and Vela. I actually fire tiles into those two if she’s up, let them tap me for about 130 points combined damage, and then finish them. So I think she’s worth taking in case they, or any other DoT reliant heroes, fire (and she sucks a ton of health off Heimdall’s heal).