Same problem here, HP DL580G7 server with NC550SFP NICs.
driver: be2net
version: 4.2.327.0
firmware-version: 4.2.401.6
bus-info: 0000:11:00.1
4 x 10ge ports and I see fewer drops on the iscsi interfaces with jumbo frames than on the interfaces used for vmotion, vmnetwork etc.