Endurance is a scourge for nearly everyone (except Blasters, cause this dev team LOVES Blasters, like, a lot), so I hear ya. Dark is notoriously end-heavy too. If you're finding DC useful now then continue using it. You can always respec out of it later when you can devote more slots to end reducers (you'll likely need 2 in every attack and toggle) and global IOs that give +end and +recovery.
Accuracy and tohit are different things. You can't slot powers for tohit, only accuracy. Tohit adds to your base % chance to hit, which results in your accuracy enhancements working better because they are multiplicative off your base. If at any point you see yourself wanting to consistently hit +2s or higher you're going to need both accuracy and tohit. Soul Drain helps with this because it also boosts tohit, but with so many critters having the ability to debuff tohit (and everything in Dark having a tohit check, which for Soul Drain is a catch-22 because you need to be able to hit critters in order to buff your ability to, um, hit critters...) you really can't have too much unless you're sticking to +1s. @Snarky is a pro when it comes to Dark Brutes. Perhaps he can give his 2 pints of blood here.