Does this game present a real concrete solo mode or even co-op mode that doesn't require a DM? Or is it basically a rough-on-the-edges one like Dungeon Saga that had many unclear dynamics and required a bunch of house rules? In other words, does it feel refined or some alternate sloppy mode they tacked on to a game that otherwise is clearly most refined with a DM?
Depends on what your problem with DS solo mode was. Star Saga is much more specific about which minion acts and who should be targeted. The nexus cards are also more specific on how to handle things. It might be less interesting for minion actions as they will likely be pretty predictable but there is a special card every turn and reinforcements every turn which might put the heroes in trouble even without optimal actions.
I think there is more hidden knowledge in the mission write ups so eye discipline might be required when setting up and reading things.