Logging Variables

I take it you're doing this in a 10.x or early 11.x version? Your code works in 11.4, so I'd suggest some additional logging:

when XML_CONTENT_BASED_ROUTING {
    log local0. "here"   
    for { set i 0 } { $i < $XML::count } { incr i } { 
        set id $XML::values($i)
        log local0. "Current ID = $id" 
        if { ( [matchclass $XML::values($i) equals DataGroup_by_Org] ) } { 
            log local0. "Sending to pool_A" 
            pool pool_A 
        } else {
            log local0. "Sending to pool_B"
            pool pool_B
        }
    }
}
when LB_SELECTED {
    log local0. "here: [LB::server addr]"
    log local0. "3189: orgName $id sent to [LB::server addr]"
}

Can you report back what you get in the logs?