How chatty is connection mirroring?

I have a U-shaped topology, 2 F5s to 2 routing-switches:

          +---------+             +---------+
          |         |             | LB2     |
          |   LB1   |             |         |
          +---------+             +---------+
            |    |                   |    |
            |    |                   |    |
            |    |                +---------+
          +---------+             |         |
          |         |             |  RS2    |
          |  RS1    +-------------+         |
          |         |             +---------+
          +---------+                   ^
               |  |                     |
               |  |                     |
    svr1 <-----+  |                     |
                  v                     +
                                        requests
                svr2

LBs are config-sync enabled, VIP is configured, and announced to each RS with a shared floating IP with LB1 as active LB. Vlans between server and clients (where requests come) are extended via link between RS1 - RS2. EBGP sessions are established between each LB - RS link. Tests conducted fine requests to VIP is forwarded to svr1,2. But to keep the TCP connections between clients and servers, connection mirroring is enabled to test LB failover. However, every time i have connection mirroring enabled, the server vlan becomes very chatty between LBs, thus the link RS1 - RS2 now carry extra traffic. The failover works just fine, but I see the throughput: OUT = 2xIN due to this. Is this expected behavior? If it is, what's the alternative? a separate link directly between LBs?

Thanks!!