switch host different VIP port

I may be missunderstanding the question but based upon what you already have in your iRule maybe something like this is what your looking for:

when HTTP_REQUEST { 
    switch -glob [string tolower [HTTP::host]] {
        "url1.domain.com" {
            pool Pool1
        }
        "url2.domain.com" {
            pool Pool2
        }
    }
}