I maintain my own bikes, for tours and general riding I carry a
Park MTB3 Rescue tool. It does what I need. If I have to overhaul something on the road, I am going to find a fully equipped bike shop or cut the trip short and go home to my fully stocked shop. I realize this may not work if you are on a world tour a thousand miles from home. I have toured mostly in the US for 30 years off and on. I have only had one trip cut short by a component failure and that was a frame breaking. When I first started touring I used to carry a 15# penalty in spares and tools. Not anymore. In this day of overnight service, internet access and good quality equipment I can just about get a complete bike overnight if the need arises.
Aaron