Now we're talking, drivers are definitively the major issue here.
Intel pre-release driver: intel-nvme-1.0e.0.0-1OEM.550.0.0.1391871.x86_64.vib , did the trick.
The results are still a bit strange when it comes to write/read performance and the scores / values are still not 100% where I want them to be, but ATTO finally shows sequential results way over the 600/800MB limit I was seeing with vmwares driver.
Anvil's Storage utilities still shows low score both on LSI_SCSI and paravirtualised driver. I'm not shure why, but the results are way improved.
I suppose gold release of the driver, and maybe a combination with ESXi 6 will improve this more.
I will still investigate a bit more.
intels pre-release driver with LSI_SCSI controller:
