My potted hibiscus and mandevilla are affected. I have used Orthene, Cygon, Thiodan, and Di-syston. The Thiodan and ultrafine oil spray was effective but not for long. The yellow sticky traps worked but filled up very quickly . It sounds like you have used everything but the atomic bomb on your plants.
Insects can become superbugs with repeated sprays of insecticides as they build up resistance.
Your impatiens and mandevilla are high on my DO NOT plant list as they have lots of problems. Hibiscus also have problems but usually are more manageable. They are usually big growers to 10 feet plus and resent confinement in a pot for more than two years for the standard landscape varieties. I would plant them in the ground and use something like desert rose as a substitute. If you insist on fiddling around with these troublesome plants you might try a mix of Organocide and Excel which is an organic oil and pyrethrum mix.