Here are a few ideas:

Artic Mullein (verbascum)

Moraea bicolor

Tall bearded iris reblooming varieties, Forever Gold, Bayberry Candle, Harvest of Memories

Spuria iris (wonderful bronzes, golds, etc. but they get tall)

Daylilies

I love the color of yellow kangaroo paws, especially when they are backlit. My mom's didn't do well this year either, so maybe it was just a bad year for them. I have never been able to keep the yellow ones healthy, though.
Good luck.
Renee

Anigozanthus 'Harmony' may be an easier yellow flowered form to try, as with all of them, they can be difficult to establish in hot weather as the roots can dry out too quickly before they get rooted in. A month into the winter rains is usually a great time to get them established, avoid under and overwatering. Other yellows to consider in the same vein of taller yellow flowers might include Achillea 'Coronation Gold' or Bulbine frutescens, or one of the yellow flowering forms of Alstroemeria.

Thanks very much for your suggestions. We did plant the kangaroo paw in early July. Right now they look incredibly sad looking :(