I'll keep poking around. I don't think it's the cabling since it is on a blade server and its sister node is running fine under Windows.
Found the setting for jumbo frames on ESXi and that let me get to 2k MTU. Either it's ignoring the opensm setting for 4k MTU or my opensm isn't pulling the partition config properly when starting up. Guess I should look up if there is any documentation for the 2.7 firmware on 4k support.
Thanks for your input, moving forward we'll probably be using more recommended hardware so hopefully that clears up some of the issues.