I can't recommend that many "really high-end" cigars that are mild-to-medium flavor, but if mere premiums will do I have a few suggestions.
Macanudo is very well made, mild and very consistent within each of its lines. I'm fond of the Cafe and Maduro, also the Vintage years. Vintage 19688 is very good IMHO.
H. Uppmann original is pretty nice.
I'll echo the recommendations for Montechristo original and White.
The Arturo Fuente 8-5-8 is a mild-to-medium introduction to that brand.
And I am very fond of Romeo y Julieta 1875 -- tasty but not overwhelming.