Well, if you're only taking HHD because you think it's going to help you with Psychology in Uni, then it would be a waste of a subject.
Sorry I just looked closer at your original post and saw you're taking Psych 3/4 in Year 11. Keep that, don't bother with Year 11 Psych, it's easy enough to pick up at uni anyway. Honestly though, I don't think 7 subjects is a good idea unless you're aiming for 99.95... Not having your worst subject count is pretty pointless, the difference in your ATAR between taking 6 or 7 subjects might not even be noticeable. Depending on the range between your 6th and 7th... your ATAR might not even change. So, a whole extra subject for potentially the same ATAR. What you could do with the time you would have invested into your 7th subject is just invest more time into the other ones and get higher scores in those.
Looking at your subjects, I'd keep your plan exactly as it is but just drop HHD and do 6 subjects instead. (If it makes you feel any better, I did 1 subject in Year 11 and only 4 in Year 12, for a total of 5)