Internet Proxies load balanced through LTM

Has anyone tried to load balanced the internet proxies through LTM ? We have configured our proxies to be load balanced through LTM. It works fine when users are surfing internet & watching videos. But we hot with a very strange issue when people using outlook in office 365 (Mailboxes in MS cloud), a lot of people complained that their mailboxes hangs or frozen. At the same time several people complained that they are unable to access the internet. All this traffic works fine when proxies are load balanced through DNS round robin. Any thoughts or suggestions ? Below is the VS & pool config.

ltm virtual vs_proxyserver_prd_8080. { destination 172.27.116.124:webcache fallback-persistence source_addr fallback-persistence-type source-address ip-protocol tcp mask 255.255.255.255 persist { cookie_proxy { default yes } } pool pool_extdmzproxyserver_prd_8080. profiles { TCP_RAC { } analytics { } http_proxy { } } rules { irule_inserted_x-forwared-for } source 0.0.0.0/0 source-address-translation { pool SNATpool_proxy._8080_PRD type snat } translate-address enabled translate-port enabled vs-index 269 }

ltm pool pool_extdmzproxyserver_prd_8080. { description "McAfee Proxy Servers in External DMZ" ip-tos-to-client 32 load-balancing-mode least-connections-member members { nds_ext_beseh011.:webcache { address 172.27.119.106 connection-limit 24000 description "McAfee Proxy Servers in External DMZ" priority-group 10 session monitor-enabled state up } nds_ext_beseh018.:webcache { address 172.27.119.101 connection-limit 24000 priority-group 10 session monitor-enabled state up } nds_ext_beseh019.:webcache { address 172.27.119.102 connection-limit 24000 priority-group 10 session monitor-enabled state up } nds_ext_bxteh011.:webcache { address 172.27.119.108 connection-limit 24000 description "McAfee Proxy Servers in External DMZ" priority-group 10 session monitor-enabled state up } nds_ext_bxteh018.:webcache { address 172.27.119.103 connection-limit 24000 priority-group 10 session monitor-enabled state up } nds_ext_bxteh019.:webcache { address 172.27.119.104 connection-limit 24000 priority-group 10 session monitor-enabled state up } } min-active-members 1 monitor min 1 of { gateway_icmp http_8080 } service-down-action reselect }