ip.fastpath.enable ensures that the filer responds back on the same interface that an incoming request comes in on. That means disabling fastpath causes the filer to rely solely on the routing tables;make sure all of your routes are correctly configured on the filer and you should have no issue. I have not had that issue with any of the servers we have connected. Almost all of our servers use HP NIC teaming and none of them have shown any adverse issues. We have fastpath enabled on all eight of our filers.
I remember an issue at a previous employeer about issues with a Cisco Nexus 10GbE network and fastpath. I know we disabled it until patches were applied, but I don't remember if they were to the switch or the clients.