Wouldn't any draw in any finite deck be bounded linearly by the size of the deck (unless you're executing a KC-gain combo)? Under this criterion, Crossroads wouldn't be exponential.

The way I would do this rigorously is to define the draw growth of a card c as follows: c(n,k)=max (over all finite decks D without any c's, multisets of cards K with size k, none of which are c): cards in the hand after starting with n c's and K in hand, and playing only c's.

Then,c(n) is the max over k the growth rate of c(n,k) using traditional asymptotic analysis. Crossroads is exponential in this circumstance.

Now for something to be unbounded, it would mean that for any function f:N->Z, there exists a k where c(n,k)>f(n) for all n (which means c(n) has to be undefined).

of course, c(n,k) is undefined for Scrying Pool for all n in Z+ and k, so it would be unbounded.

Counting House is also unbounded in this criterion.