As Embury says, there's some sense in using a Scotch-based liqueur, and although this version of the Bobby Burns is rarely seen, it's worthy of a trial
My ratios are 2 parts scotch (JW Black works well), 1 part Cocchi sweet vermouth and 1/2 part D.O.M. But last week I absentmindedly grabbed the Drambuie instead. Didn't realize my error until well after finishing what was a delicious cocktail. I guess next time I'll just reach into the cabinet with my eyes closed ...