We will need to see a few more pictures for a better diagnosis.  Please cut off a few of the severely affected branches & put on a surface for close up pictures of the wood and the leaves.  Try to also get a few pictures of the undersides of some of the leaves.
Right now the candidates are fire blight, mites on the leaves, or a wood rot such as black rot.  Pear psylla is a possibility as well.  All of these can cause extensive blackening of leaves.

Thanks for the additional pictures.  My best guess is that this is European red mite damage which can cause blackened leaves. The fact that the mid veins of the leaves are still green points away from fire blight as a cause.  Usually there are tiny white mite molt debris but rain may have removed these.  I suggest you examine the larger limbs associated with the black leaf areas to look for cankers.  If it is mites, there should not be cankers.  If it is indeed red mites you might look into applying a dormant oil spray next spring.  Usually mites do not endanger the overall health of the tree.