Typical summer hydrangeas, in my opinion. Looks like a combination of leaf scorch (from sun) with a little insect damage mixed in. You can crumble the dry leaves up for mulch. I have a few that look a lot worse than this. All you're looking for is enough healthy leaves to keep the plant healthy - so if the whole plant looked like that, I would seriously consider moving it into more shade and spray it with insecticide. Schultz makes a good fungicide/insecticide combo that has worked on everything I've tried it on. Looks like a fair amount of winter dieback, though, so if it's not a new-wood bloomer I wouldn't expect many blooms. You can get rid of those bare brown stems though to keep the plant neat.

Sometimes a curled-under leaf will reveal a nursery web spider (which are quite large, but harmless) and her spiderlings.