The 690 has been refined into a very good engine, with larger oil passages and improved rocker arms/bearings. Rocker arm bearing issues are far less common, and camshaft failures are in the past. Of course, wheelies and stoppies can affect oil flow to the cylinder head. Infrequent oil changes are a real problem, as is running the oil level low.
You are correct, nearly all oils with a wide viscosity spread will contain significant quantities of viscosity index improvers. And even the highest quality VII's will shear down in motorcycle use. It is good to note that oils with VII's revert to the base oil's film strength under high loads and a 10W-50 will not match the extreme load carrying capability of a high quality 50 viscosity oil.
Oils with high HTHS are worth considering for engines with known oil related failures. I tend to like Mobil 1 20W-50, with its high HTHS and robust shear resistance. It is probably the most robust commonly available oil, anywhere. Yes, I know it is a V-Twin oil, but there is nothing unique about it, other than very high quality base stock and a very normal, robust additive package.
Regardless of oil choice, change it frequently.
