Which level 4 monster is the best?

vampires, of course! Then probably the Crusaders. Regarding the snipers: since there's an Arctic and Lava sniper of level 5 in Haven, it's logical to consider regular snipers as level 4, but I would classify them as very strong units of level 3. As for golems, for example, there's a Diamond Golem of level 5, so a Gold Golem should be level 5 without any upgrades. And by the way, a golem can easily defeat a vampire! (It seems vampires haven't learned how to feed on gold yet). The sniper should probably be level 3, while wizards are level 5, and the difference between a Sniper and a Wizard is very significant!