Wax myrtle can be brittle and lose limbs. It will also lose lower foliage leaving bare holes in your screening. The ones down here are a pain about sending up sprouts.

Have you thought about some of the viburnums? I am sure there are some that would do well in your area.

Viburnums are nice plants. Are there some that are evergreen? The ones I've seen are all deciduous.

V. Odoratissum, Tinus, Suspensum and Awabuki (or Awabuki Chindo) are all evergreens and make terrific screens. Not sure if they will do well in your area however. You might want to look around your neighborhood and see if anyone is growing them.

Leyland Cypress wouldn't have worked anyway. We tried it as a screen and it grew too sparse in the shade. While shade isn't ideal for wax myrtles, we have some growing in woodland conditions and they are quite thick. If you have enough room to layer with lower growing bushes in front, such as rhododendrons, to patch any holes it might work very well.