No, you definitely hit the mark
I especially like the segment that starts at 1:10 and 2:50. It might not be my absolute favorite boss music ever, but it's not bad for a start. Definitely liked the use of the bells, gives a very ominous feeling. There was one instrument that I wasn't fond of. The synth that plays alone at about 1:30. I'm not saying it wasn't a good choice, there are several parts of the song where it sounds really epic and I absolutely love your use of that instrument, but there were also parts where it didn't fit as well. Particularly that part around 1:30 where it's playing alone, that didn't sound good. I wish I had the terminology to describe what it is I didn't like about it, but alas I don't. I guess when it's alone, it sounds a little too "buzzy" if that makes any sense. One other problem that I saw with the song is that it doesn't loop. It's listed as a classical loop, but it doesn't loop. It's a boss theme, it has to loop! Well, in my opinion it should. In a real boss battle, nobody wants the song stopping in the middle of the battle, and I doubt the battle will last exactly 3:20, the length of the song. Also, the song wasn't very classical. It has classical elements, but uses a lot of synth. It is possible to have a really epic boss song that is entirely classical. Just listen to some boss themes from Kingdom Hearts, for example. On the other hand, if this is what you were going for, that's fine too, I just wouldn't label it as classical. Anyways, this was a good boss song, I hope you make more!