Mate, you know Jul 'Mdama's faction is considered the largest and likely the most powerful post-Covenant remnant in existence. Claiming that the Dark Covenant is almost or as powerful as the original Covenant Empire is neither realistic nor canon-abiding due to how vast the Covenant Empire was.
I'd recommend you tone it down and consider what you really want the Dark Covenant to be. You can still have a great threat in the form of a Covenant remnant even if its small. But it can't just be another Covenant Empire. Distant Tide: Hunter - Killer