I do think Prometheus is more than one person. The "reveal" we got this episode doesn't even remotely explain how Prometheus got access to any of the old Hood arrows that the SCPD had stored away nor does it explain how Prometheus found out Queen was the Arrow, or how he found out about The List.
Oh, she just used the Malcom Merlyn door? Makes sense.
Now I need a blueprint of the Arrow Cave were we see a "Totally Secret Door" which may only be used during really important plot reasons.