Archviles should be used as an immediate threat. They work well when the players are aware of their position, so they can prioritize in killing them. And yes, they are better off running free. The boring scenario you're talking about is when they get teleported in an area you've already cleared, without seeing or hearing them, so when you later get back to that area, everything is resurrected. That is a shit scenario, and i agree, that it's better to be avoided.
In Treehouseminis' map the placement is trash, because the archviles serve no purpose other than to waste your time. They don't add challenge to the fight with the HKs on the platform (the fight before you can reach the viles), because you have plenty of space to attack the HKs, outside their line of sight. Then the archviles only serve to delay you from pressing the button that triggers the next encounter, and there's no logical reason for this time waste. The archviles might as well not be there, they are useless and further destroy the pacing, which is already pretty bad in this map.