Thank you for the suggestions. Do you think the hydrangea is going to be okay based on how it looks? I'm worried it's too far gone...

No, it actually does not look too bad but, after you have searched for and disposed of these pests, add some mulch up to the drip line so the soil conserves moisture and does not loose it to evaporation. It may be too late in the growing season to produce a full flush of replacement leaves so the plant may wait either until next year or until the Fall when Summer temps moderate and come down. Quickfire and LQF are pretty sturdy plants. I have one LQF handling 100+ degrees daily temps very well (with extra watering of course). I would remove the rocks as these pests sometimes hide underneath all kids of stuff.

Thank you for giving me hope! I removed the rocks and added some mulch so maybe I will see some improvement. Thanks again for your advice, much appreciated!

Iron phosphate slug bait such as Sluggo is nontoxic to other critters. It might be worth putting some around the hydrangea along with hand picking.

The leaves that are left look good and considering that the plant was planted, attacked by slugs, and then transplanted, I think it looks OK. Next year should be better.

I've been using beer traps for about two weeks now as well as going out & picking them off. There are just so many of them! Yuk! I'm getting some Sluggo next chance I get! Thank you!

Two of the branches that were hit hard have lost their leaves with no signs of new growth yet. Do I just leave them alone or do I prune?

Leave them alone. No plant in its right mind would want to develop new growth in the middle of the Summer. Wait for new leaves when you get cooler weather in the Fall or wait for new stems next year.

When I had a plant loose all leaves due to water problems some summers ago, I left it alone. It did not put new leaves or new stems in the Fall but it put new stems/leaves in the Spring.