The WMI/RPC issue discussed above affects polling Windows servers behind a firewall. This (and a few other reasons) is precisely a SAM agent option is being developed
SAM 6.2 Beta - Because Sometimes You Feel Like A Nut - Part 2
The QoE sensors actually leverage the first cut of this agent technology. The agent hosting the QoE sensor initiates HTTPS communication to the assigned polling engine on port 17778.