Thats pretty silly that it can be. It reminds of the old days of Brood War where you had to kill Fenix in a zerg mission and he has 800/800 hp, and you can just use broodling and one shot him with a queen.
For such a big single unit investment, you shoulndt be able to one shot it. Just like you cant graviton ultras and thors, you shouldnt be able to abduct the Mothership.
Should also have some more armor, being a city and all.