She's actually more capable and dangerous when she's away from the Joker, which has actually been most of the time since she's been in the DCU.
With Ivy, it's more a comedy team, with Ivy (and Holly) playing straight man (so to speak), the Hardy to Harley's Laurel, the Abbott to her Costello, the Martin to her Lewis, etc. And, of course, Batman's played that role with her. But that's for a later post... :)