In the first part you are heavily disadvantaged. You are fighting enemies with maximised equipment, weaponry and skillsets, while having yourself hardly any equipment, decent weapons and before all hardly any of the good skills. And no I'm not talking about voidlings, voidlings are kind of most boring enemies in the game, I'm talking about level 3 and 4 enemies. Because of the armor system you feel it even more.
The fact how leveling inflates the numbers, just makes it worse. One level up gives you about 50 HP more even on the low levels. Having 25 or more % more life just because of a level up just feels off.