No one has answered this post so I thought I would give it a try.
I grow hibiscus and they really should not drop all of their leaves. Make sure you are not over watering. Hibiscus can be kept as a houseplant but will not bloom unless you can give it a lot of light.
Check the leaves for aphids and white flies. They often attack hibiscus outdoors but will be happy to attack a stressed plant indoors.
Pruning a hibiscus can be done to rejuvenate the plant. However if it is in the house and in a relatively low light spot, I'd wait until Spring so as not to stress them more. They need all the leaves they have to produce food.
If the plants are in a well lighted spot and especially if you can see new leaves appearing on the stem, it would not hurt to cut them just don't cut them too low.
Hibiscus should be watered well but no water should be left standing in the saucer or you may get root rot. Hibiscus should get a weak soluble fertilizer with each watering. Hibiscus will take less water in cooler weather. Hibiscus outside can handle being almost dry.
Happy gardening in Hawaii. Gardens are where people grow.