Sync IIS servers, excluding some sites.

Problem;
We are currently syncing our CA (content author server) to our CD's (content delivery server) using web deploy.
We have a large number of sites (400+) and some sites have to be excluded from the sync.

I am looking for a way to speed up the process as it currently takes about 20min to sync all the sites.

I am doing this with a PowerShell script that just loops through the sites skipping anything in the exclude list.

$sites = Get-ChildItem IIS:\Sites -Exclude $excludsite$msdeploy ="C:\Program Files\IIS\Microsoft Web Deploy V3\msdeploy.exe"
foreach ($site in $sites) {

I would really love to be able to just sync all of IIS except a few sites as I have seen how much faster it is to use the 

Sync-WDServer

vs the

msdeploy.exe -verb:sync

I tried moving the sync task to a PowerShell job and syncing lots of sites at the same time but if anything that seemed to be a little slower.
Looking at testing out 

Sync-WDSite

but this is still going to require looping through each site one by one and original tests had settings issues.

Any tips/idea’s would be appreciated.