I got the first older Nyssa trilogy at the tail end of a subscription starting with Castle of Fear. Sadly, I think the starting and end trilogies to that subscription are worlds apart.
I found both Cobwebs and Whispering forest incredibly dull. The later was just entirely unengaging, but the form was actually annoying. The idea of Nyssa meeting the Doctor again in later life is great, but they squandered the potential. There is very little time given to the TARDIS crew interacting and the Doctor and Nyssa exchange very few words before being separated again.
Thankfully the ending trilogy for the arch is wonderful with Equilibrium being a true high point.