You could use the Nautilus offensively, enchanting an opponents creature to make it easier to kill
The purpose of blue's polymorphing is not that it uses it as kill but that it has the ability to change it from one threat into another
In a lot of cases, this is going to feel like a green Sphinxs Revelation with how it single-handedly gets you back in the game
(And, of course, the sweet spot is when you have very strong tribal rewards and very strong individual creatures!) Sometimes you might have to play a couple creatures that are just below the bar of normal playability, but you certainly don't want to fill your deck up with those
Vindictive Vampire 4 mana is a lot, but in sacrifice decks, sometimes you really, really need one more card that drains and gains, and Vindictive Vampire is happy to be that card if you need it