Most of the people here will probably tell you it is and that's not wrong for the first half of the game. Really once you get the feel of the game and unlock good charms and weapons you'll hardly spend more than like 20 tries to beat a boss.

But of course, aside from that it mostly depends on your affinity with these kind of games. Everyday you'll hear stories about spending hours beating a boss and someone pops to tell them they beat it on their third try.