I am no expert but I have been around muscovy ducks for over 15 years. I light hen is more than a formidable prey for a MRT. Double a hawks size and as powerful as ducks get. A drake may not be a speedy duck but if you take one with a MRT then my hat is off to you. I've seen drake muscovy ducks kill fighting roosters and even hen turkey when protecting an area.
I wouldnt say formidable hard to kill yes, thats like comparing a 8lb tame rabbit to a cottontail or a big white leghorn rooster to a pheasant the tame one is harder to kill but not much of a flight to watch its more or less a battle.