Got bored with it, TBH.
You spend nearly all of your time defending your base, not helped by the fact that the city guard are both useless and stupid, and your heroes pretty much do their own thing despite your "orders".
And as mentioned, there are some massive jumps in difficulty a few missions in. Get one novice (training) missions, two amateur (or similar) then it quickly jumps to "advanced", which are fairly tough.