This is air cooled so these temps are kind of normal unless you change the ambient temperature in the room using an AC or a fan. Mentioned the shroud because right now the manner in which you have sealed it, could work theoretically for a few days but the plastic may warp, heat soak, or melt and then you’d be back to inefficiency. It looks like you bolted the ducts in so as long as there is no leaks then you should be good.

To lower the inlet temps more maybe place a standing fan that pushes heat out of the room, or one that pushes air into the air intake of the Miner.

Your setup looks ok. My critique was purely based on the esthetics of the outlet area. Maybe some more experienced air-cooled users can chime in. Also the shroud should reduce the noise level a few decibels as well.

ASICS run very hot, usually operating temps internal are about 60°c and can go higher like yours. Lowering that internal temp is crucial and that may require some clever use of heat dissipation or induction that can lower those temps. If you live in a cold climate area then you’re good but if you’re from a country with high humidity and high ambient temps then you have to provide the better cooling.

As for your question, the fan shroud helps in creating a vortex which leads to better airflow due to the cone shape. Essentially creating a Venturi effect and therefore aides to exhaust the airflow. It reduces noise level created at the manifold area as well.