Right. A good way to think about Death Gaze is that it effectively doubles the damage you deal. It's also really good against enemies with Death Protection, since it'll take out a level on it's own, then the normal attack will take out another.
In terms of general strategy, you always to prep Health->Attack and +10% badge so that you can offset her -50% attack. As for locker items, your best bets are usually a source of resistance (e.g. Dragon Shield) or Whurgarbl. The former for a melee-based poison strategy, the latter for a more Fireball based strategy.
Just be careful since there's a bug with Burning and Poison, where hitting a monster with Whurgarbl and a Poison strike will only add poison if it already has burning.
In terms of overall power, she's pretty strong but has been hurt a bit by the changes to various enemies to do magic damage. I'm still holding out that either her attack penalty is reduced slightly or she's given 25% magic resist.