Thin Blood Confusion

Just played the first thin blood deck with the starter deck.  The thing that confused me most was the Blood potency rule.  If you have to have a character out with equal or higher blood cost, why does the Thin blood deck run a bunch of 4+ BP cards when they dont have a single character above 3 bp?  It really confused us.

Thin Bloods seem to be about bringing other Characters down to their level with the -1BP tokens.

This can even take characters out of the game if they stack too many...

What's more, reduction in BP can mean you won't be able to use select cards in your deck if their BP cost is now too high.

Thin Bloods also have a number of ways to increase their blood potency for playing cards. All the 1BP Vamps give the 2 and 3 blood Thin Bloods +1BP while attacking, and I think there's at least another card that can boost it for certain things.