I would tell you wait at least till next expansion. You said they killed off combo druid and even though I disagree to some extent (weak but not dead) I see your point. However if in April the next set revives it you may regret any disenchanting done. I do appreciate that you have a plan on what to craft. Seeing it well thought out is a good start. Still I'd wait and see if it were me. I'm sitting on my dust now for the same reason.
Also with rotation comes the Hall of Fame move. That will collect you some dust as well. Whatever card they are moving craft it as you get that dust back. That's how I round out my collection as F2P*. I've been F2P since the start and can make a deck of each class that I enjoy. I definitely don't have all the cards I want but I accept that sacrifice. Besides at rotation I tend to be able to craft 1 or 2 legendaries per set so I end up with enough to play around with.
So again I'd just say wait. See what moves and what comes out. These cards aren't going anywhere so you have that dust in bank anyway. See what the future holds then do what you will. Good luck!
*I had to buy that Wild bundle. Was too good to resist!