Alcea rugosa (Russian Hollyhock) is simply THE BEST Hollyhock. Like you said, it is completely resistant to rust, aphids, and other nasty things. I can not stress enough how wonderful it is. If you have not had luck with Hollyhocks before you must try this one.
My old neighbor had one of these in front of their shed in full sun. It got four feet wide and probably seven ft. tall or more. The yellow blooms are beautiful, and the foliage is more devided than the regular round leaves of normal Hollyhocks. Theirs must have produced babies from the main plant because it bloomed every year.
I just bought one this year. Gorgeous and not fussy. Its still pretty small though, as it is in a particularly neglected site. I should get much bigger next year, and even more beautiful.
CMK

Yes, I've grown them and they are marvelous. Unfortunately they are not snail or slug proof.

I haven't grown them. Perhaps I will try. The only yellow I've grown is Charter's double.

Libby

Alcea rugosa is a rust-resistant perennial hollyhock, but comes in yellow only. Alcea ficifolia (fig hollyhock) is another rust-resistant perennial hollyhock, but blooms in colors of rose, yellow, copper, white, red, and burgundy-purple. Has anyone grown this variety?

I have grown a peach colored ,figleaf Hollyhock. Growing the yellow Russian h.hock this yr.