It's all about incremental changes. For starters, don't change the drop rate. Keep it as it is, but change medium map to be like low map where it can be solo'd. Essentially there should be 2 categories of maps.
Low and medium: Can be solo'd. Does not drop legends. Even the rings it drops are not valuable (no one loots them anymore). Drops sards which new players need, so it makes sense that they should be able to solo these maps.
High, Chaos, Insane: Recommended to be done in a party. Drops legends, which veteran players need.
Currently the medium map is in the second category, which is clearly out of place.
I suggest the reworked medium map to follow the same model as the low map. A couple iron golems, etins, minos, and one mini boss (Succubus). I chose succubus because the hitbox will make it fairly easy for a wizard to solo, compared to something like a fatal skeleton. Also, red dragon