I doubt VMware is testing all the driver and firmware version combinations for each IO device. Even the note on HCL states "Firmware versions listed are the minimum supported versions". Moreover, the HCL does not always list the FW version of lot of ethernet controllers (refer the attachment).
By relying on Dell FW ISO, we are not completely in uncharted waters. As the expectation is Dell has tested and certified the Firmwares for the operating systems listed in their support release document.
Again this is not an ideal way and Dell should seriously consider publishing a supported driver and firmware matrix with each (point) update to ESXi or Firmware repository.
