Exchange 2010 ActiveSync Problem

Hello, we're running Exchange 2010 in a 3-node DAG (all-in-one mailbox servers), and have noticed some problems - specifically sporadic delays, up to 20-30 minutes, with ActiveSync, only on iOS devices (Android/TouchDown is fine). I've been working with engineers at Microsoft, and they believe our mail system is OK, and are questioning our persistence settings on the F5 - running v10.2.3. They have seen connections from the iOS devices bouncing between the CAS servers when they should be sticking to a single server. When I take a look at the F5 statistics, I'm not seeing any hits at all - ever - on our ActiveSync pool, which makes me think the AS connections are likely hitting a different pool and possibly being impacted by its persistence settings. All other pools have statistics to support usage. When we first configured the default iRule, we had some trouble getting ActiveSync to work, and ended up adding a "/" after microsoft-server-activesync, and that seemed to resolve the issue. Of course now I'm questioning whether that was the right thing to do. I've pasted the persistence, followed by the append iRules below. Any thoughts at all would be appreciated.

Persistence:

when HTTP_REQUEST {

     Offline Address Book and Autodiscover do not require persistence.

    switch -glob -- [string tolower [HTTP::path]] {

        "/microsoft-server-activesync/" {
             ActiveSync.
            if { [HTTP::header exists "APM_session"] } {
                persist uie [HTTP::header "APM_session"] 7200
            } elseif { [HTTP::header exists "Authorization"] } {
                persist uie [HTTP::header "Authorization"] 7200
            } else {
                persist source_addr
            }
            pool Exchange__single_as_pool
            COMPRESS::disable
            return
        }

        "/owa*" {
             Outlook Web Access
            if { [HTTP::header exists "APM_session"] } {
                persist uie [HTTP::header "APM_session"] 7200
            } else {
                persist cookie insert
            }
            pool Exchange__single_owa_pool
            return
        }

        "/ecp*" {
             Exchange Control Panel.
            if { [HTTP::header exists "APM_session"] } {
                persist uie [HTTP::header "APM_session"] 7200
            } else {
                persist cookie insert
            }
            pool Exchange__single_owa_pool
            return
        }

        "/autodiscover*" {
             Autodiscover.
            pool Exchange__single_ad_pool            
            return
        }

        default {
             This final section takes all traffic that has not otherwise
             been accounted for and sends it to the pool for Outlook Web App
            if { [HTTP::header exists "APM_session"] }  {
                persist uie [HTTP::header "APM_session"] 7200
            } else {
                persist source_addr
            }
            pool Exchange__single_owa_pool           
        }

}
}

when HTTP_RESPONSE {
    if { [string tolower [HTTP::header values "WWW-Authenticate"]] contains "negotiate"} {
        ONECONNECT::reuse disable
        ONECONNECT::detach disable
         this command disables NTLM conn pool for connections where OneConnect has been disabled
        NTLM::disable
    }
     this command rechunks encoded responses
    if {[HTTP::header exists "Transfer-Encoding"]} {
        HTTP::payload rechunk
    }      

}

Append:

when HTTP_REQUEST { if {([HTTP::uri] == "/") } { HTTP::uri /owa } }