Aw it IS proxmox. Yes that is 100% the issue. Try either a different driver OR pass through the entire NIC port. Everything else would work as most other things are generic, netmap/suricata needs specific driver support, HyperScan doubly so.
Edit: SR-IOV is the best driver for this card and will allow full pass-through as you stated, try that and report back on any improvements...
Edit: SR-IOV is the best driver for this card and will allow full pass-through as you stated, try that and report back on any improvements...