The story is the dev privilege.
If you don't like it you don't have to play it.
If the same seem to easy for you, you can increase the difficulty. Difficulty management is hard for every developper since lot of peoples with different levels of skill will play the game. If you set the default difficulty level for experienced player of that kind of game, you'll make it impossible for a lot of players to play the game.
Opposite and peoples cry that's too easy.
Dev will enver be able to please everyone.
After that, I don't know how many stage you played yet. Yes, goblin are weak. Yet with the placement and number, they can be a bother. It's hard to be killed by them, but you'll quickly find map where they'll often be in position to land a few hits if you try to bash you way through. Meaning you'll be weakened when fighting stronger enemies / boss.
I've been playing on normal since I haven't really played that kind of game in a long time, and the first difficulty I've seen was when I reach the dead town. (well, except the boss, it's more enemies that really where a bother and dangerous if rushing). That's like 1/3 of the default number of stage. So, yeah, it take time for difficulty to kick in (in normal difficulty) but that that much time I have to get use to the gameplay...