Bear in mind that the enemies you mention are among the hardest in the game. I count myself as experienced but I find it very hard to do Oryx 2 with a Knight so I rarely get SB, struggle in Shatters with a Knight and find Tomb hair-raising. The only one that is straightforward is Oryx 1, with at least some other people as I would not like to solo it with a Knight.
So if you too find these hard don’t worry too much about it. Save playing them for when you have a ranged class, or a class with a ranged ability like Assassin or the bow classes. Use the Knight for what it is good at, shrugging off damage before walking up to gods and bosses to stun them.