What were your expectations for Heroes 4?

Uh, you're getting something wrong... A castle has fewer chances against a fortress than the other way around. I'm a newbie in Heroes 3, but the Swamp is one of the best starting locations...

Correct, Zubr, correct. This is just a comparison of the equivalence of starting conditions. It's even comparable to the color in chess. Starting conditions are starting conditions, no matter what the game is called. And what the game focuses on is a secondary matter.

In Heroes 3, a lot depends on the starting conditions, especially considering that fixed maps are used much less often than in Heroes 4. Or rather, Heroes 4 doesn't have a proper generator for such maps:)
Therefore, in Heroes 4, the variance in starting conditions isn't as critical; usually, it's artifacts, Dryads, and neutral monsters, which don't always affect how easily they can be defeated by the forces of a specific castle. In this sense, perhaps only the Necropolis with its vampires stands out; by getting 2-4 of them, you don't even need to think much in battles with living troops of levels 1-2, but this is more of an isolated case.
Although, maybe I misunderstood something about the starting conditions.