I too have got psoriatic Arthritis & have been living in Perth for almost 2 years.
My arthritis & Psoriasis have been loads better since I've been out there & I've reduced my strong Arthritis tablets to half & cut some of my others out.
I have been back in the UK for 6 weeks for a holiday & both my Psoriasis & Arthritis have got a lot worse, can't wait to get back to sunny Perth.
Perth is a dry heat unlike Queensland which is humid, so I'm not sure if the humid temps will suit you. I only have knowledge of Perth.