The problem is that is has turned brown, if it is dead it won't matter how far you cut it back. Otherwise I have seen these closely sheared without it fazing them.

There are still parts that are alive and I plan on cutting off the brown parts. That's a lot of the plant though which is why I was wondering if it would recover if cut back significantly.

I would leave it be until leaf out next spring. Sometimes much more is still alive than you realize.

I have had my very large wax myrtles showing browned branch tips--just on the branches that were not pruned. Branches which were pruned the previous year are just fine. Weird, but not killing them.