Thanks for the really detailed response! We really appreciate it!
Card-artifact synergy is very important to the game. I think you thought the melee attacks were weak because you hadn't seen much of the artifacts that could improve them. Melee cards tend to have low or even zero mana cost, making them particularly useful for taking out summons. Also, cards like chop or scorpion swing can also dish out high damage to the boss if you get near enough to land all their projectiles. It just takes some careful artifact choice and maneuvering. Generally though, I do think melee attacks could still use some buffs.
Though, you were right about the gravedigger. His particles were too big, especially with the "great boulder" attack. We noticed it after uploading, which was too late lol. The butcher, though, was meant to have really large melee attacks. It's kinda his thing, so the player just best stay away when he gets near, which is generally the rule of thumb for bosses with melee attacks. Alternatively, you could steal the artifacts that make them dangerous (for the butcher, the bonesaw, rune knife, and ceremonial shears really boosted his slash area), making them more manageable while also making your melee attacks a lot more effective.
Regarding the environment objects, dashing actually allows you to pass through them, if you didn't notice. Also, some artifacts can increase your movement speed and max stamina, which could be helpful for bosses like the hairbeast, though I personally think good spacing and timing is a bigger factor. Taking advantage of the invulnerability frames when dashing is crucial with pounce and ram attacks.
If you like, you could watch the gameplay videos we posted so you could see how we personally played the game! Our personal best (which was not recorded, unfortunately, but here's a screenshot) was using the creed of obsession!
Thanks again for the feedback! Given that the game is basically still in development, it's so helpful to hear other people's experiences!