Don't have time to tear down and completely rebuild valley, so I am just outlining changes that were made since the recent patches. Smashers were breaking the stairs at the old geyser build, changing to this design has fixed that, they will now stay trapped in the geyser and not despawn.
The blockoff at uneven terrain should force the regular husks to walk a longer path and preserve trap durability closer to the amplifier for later waves.
Flingers have shifted, at least in my own experience, and are now throwing from a location to the east of their old spot. Floor freeze has been moved to compensate for this.
Whitewalker has a geyser build that is also working and has fewer structures if you need to reduce your structure count. Instead of blocking the entire ramp back up under ridge, it blocks only the lower portion and recycles them below the natural terrain ridge.
The catcher under the smasher bridge is primarily for Lava to catch smashers that go through the geyser there, but it also serves to get everything knocked down a little sooner by adding the two tiles and one wall light to the south. The wall light will also reset blaster AI if they happen to come over and start beating on the stairs.