I have tried three variations of Dubonnet Rouge and gin (including this one), and I've been disappointed in each. I've used Tanqueray Ten and Bombay Sapphire. Perhaps another brand of gin will produce better results.
I've come to the conclusion, however, that the combination of gin and Dubonnet Rouge just do not a good cocktail maketh. A three rating is the best I can give any of the gin and Dubonnet cocktails I've tried.