Brian - you may want to post this on the shrubs forum, but from what I've seen of Yews you can prune them down to just bare branches and new growth will emerge. It just takes time. And more time. And a bit more time.

Taxus are some of the few evergreens on which you can do heavy pruning but it is 50/50 as to whether they will ever fully recover or be of value. Try limbing the Taxus up and planting under it. I have an obnoxiously large Mugo pine I have limbed up and underplanted with large Frances Williams hostas. They seem to thrive in that damp shade and look great with the needle mulch. I always have great respect for plants that have outgrown their boundaries.

Lower branches showing no growth usually means the bottom is being shaded from above. Best to prune in an 'A' shape (with the top of the A cut off) to allow light to reach below. My brother once hacked the living daylights out of my folks' yews (basically just stubs left) and they came back. But, as mentioned above, it took about 4 years to regain any sort of respectable look.

tj