When I lived in Bangalore, and whenever I visit there, BMTC (the public bus transport provider) has buses at least every few minutes along the main corridors during the day.
They are often crowded, but I don't think I could call the service "unpredictable", beyond the general variations that apply to all means of vehicular transport in Bangalore. Last mile connectivity though is often painful.
The service is indeed expensive, especially when one is sharing a commute with another person.
This said, I really like your summary of Bangalore.