I was unable to make it work, I started from scratch but still the same issue.
I'm using vsphere 5 (esxi 5) and it only allows to have 1 active nic (the other one must be set to "unused") per vmkernel port.
So I guess the beacon probing/nic teaming failover is not kicking in.
Hi finally solved the issue.
I figured out that I didn't need iscsi port binding after all, that's only useful for MPIO and since I'm using a single 10 gbit path I don't need that.
So I could leave the nic's in active-active with beacon probing and everything works !