Hi,
YES, downgrade to previous version is possible. you just flush the card again; this time with the other version.
i see you got the card rev'd up to 2.30.3110 (or maybe this is the "old" one). i suggest upgrading to .8000 version. http://www.mellanox.com/downloads/firmware/fw-ConnectX3-rel-2_30_8000-MCX312A-XCB_A1-FlexBoot-3.4.151_ETH.bin.zip
Also, make sure you work with MOFED 2.1 (link above). All together with these versions you should have have a good and mature SRIOV solution. if you are still having troubles then, let us know.