I cut the luxardo to 1/4 because 1/2 seemed like a lot. Result was pretty mediocre for me, and I don't think another 1/4 of luxardo would have helped. Kind of boring, and has a taste that I find a little strange. — ★★
This particular recipe may have been popularized by a modern Beefeater brand ambassador, but note that the Bloodhound is a classic cocktail appearing in Savoy. Most versions up the base gin to 2 oz and eschew maraschino.
I found this particular version to be blander than the 2 oz gin:1 oz french vermouth: 1 oz italian vermouth classic. It was not insipid, though & adding some sweetness to the classic (which may have used sugar-sweetened coulis anyway) isn't a bad idea.
Some variations use raspberries, which I'd be eager to try.