Hm, Crossroads with Nobles and Great Halls is crazy, but as tllloyd's game proves, it works well with normal Victory Cards, too. Just look at turn 17:
— tlloyd's turn 17 —
tlloyd plays a Crossroads.
... tlloyd reveals an Estate, 2 Duchies, and a Crossroads.
... drawing 3 cards and getting +3 actions.
tlloyd plays a Crossroads.
... tlloyd reveals an Estate, a Crossroads, 2 Duchies, and 2 Coppers.
... drawing 3 cards.
tlloyd plays a Crossroads.
... tlloyd reveals an Estate, a Crossroads, a Province, 2 Duchies, and 3 Coppers.
... (tlloyd reshuffles.)
... drawing 4 cards.
tlloyd plays a Crossroads.
... tlloyd reveals 2 Estates, a Mandarin, a Province, 3 Duchies, and 4 Coppers.
... drawing 6 cards.
So, it looks like there are many cards which are mediocre in many situations but can go totally crazy given the right circumstances and a good player jugding them right.
Looks promising.