Try with the changes to the Target and Initiator again with the ESX server and see if this helps.

1- one LUN per target

2- make the following changes to the targets, and initiator your ESXi 5.5:
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1. From the console, press CTRL+ALT+W,
2. Select Tuning options -> iSCSI daemon options -> Target options,
3. Select the target in question,
4. change the values to the maximum required data size (change the initiator to match).

maxRecvDataSegmentLen=262144
MaxBurstLength= 1048576
Maxxmitdatasegment=262144
FirstBurstLength=65536
DataDigest=None
maxoutstandingr2t=8
InitialR2T=No
ImmediateData=Yes
headerDigest=None
(deprecated)Wthreads=8

Doing this will reset the iSCSI connections at each edit. Please pause any hosts connected to the LUNS.