Even playing on normal I didn't make it past the first boss, tying your attack to the dash seems cool in theory but it make combat feel slippery and imprecise, which is awkward when the bosses moveset calls for precision to avoid the spikes. If you're expecting people to play patiently and only attack between moves then there should probably be longer punish windows or give the boss less health to avoid it feeling like a slog (especially on lower difficulties).
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Also, a tip, one of the key moments to deal damages is when the boss rolls towards you with any spikes on the way (feel free to look at the gameplay video too to see the rest !)
I think you tried to attack the boss while there were pikes, which isn't really ideal ; that's why you felt like it was slippery / imprecise