To reiterate, 4-provision cards should be the absolute worst cards in the game. You're mainly including them in your deck in order to make room for more expensive cards. If 4-provision cards are providing the same amount of utility and value as 5-, 6-, and 7-provision cards, why would anyone choose to play most of the cards that cost 5-7 provisions?
I listed the overpowered 4-provision cards for Nilfgaard because this is a thread about Nilfgaard, and Van Moorlehem Hunters was already being discussed; however, there are plenty of examples of cards that are too good at 4 provisions in the other factions. (e.g. Fisstech Trafficker, Street Urchins, Lyrian Scytheman, Radovid's Royal Guards, Endrega Warrior, basically every 7 for 4 along with the various units with Bond, Fisstech and all the 4-provision damage specials, etc.)