Um, because the bosses, right?
Anywho, today's the day still, right?
Block B is hard because of two bosses in particular. Slogra and Dracula. Gaibon has a relatively predictable pattern, and nearly all of Death's attacks are negated by brandishing your whip or not being in the way.
So why are Slogra and Dracula hard?
Despite the fact that he gets knocked fifty billion feet in the air after each hit, Slogra has a long invincibility grace period that allows him to get a lot of attacks in. After being hit and landing back on the ground, he can instantly open up with an attack. While the wand he uses is easy to avoid, the problem comes in when he uses the lunge attack upon landing, which not only requires timing with precision on par with Kaizo Mario world hacks, but requires you can be running away from him as fast as you can, since he lands very close to you no matter what. If you can't increase distance from him AND time your jump to dodge the lunge perfectly, you will be hit. He doesn't use this often while using his weapon, but when you destroy the weapon, he
spams the living shit out of this.
As for Dracula, he's simply just a very long boss fight. Though, some really bad situations can occur when fighting him. in particular, if you're on right of Dracula while he summons forth a tiny energy orb, you can do nearly nothing to stop the orb since hitting it will make it launch a screen-spanning energy shot attack (Which you can only dodge successfully if you are to the left of the orb due to it's energy shot pattern), and leaving it around will let it screw you up with it's eratic movements.
Aside from that, avoiding Dracula's attacks require a lot more precision than most bosses.
The stage itself is completely pathetic until you get to the sequence near the end with skeletons and the headless guys. The skeletons are absolutely relentless. The enemy placement is astonishingly well thought out unlike most stages in the game.
What sucks though is that one mistake against ANY of the bosses means you have to play through the entire stage again,