No, you don't just lose a "very small" amount of DPS, you lose an extremely large amount, and you won't even recover much MP while you're at it. The cost of reactivating Darkside will end up eating up any potential MP you could have regained through the regen you'd get from turning it off during combat (you might even actually go negative... I'd check it, but something like this is so pointless that it's not even worth verifying). And for negligible to potentially negative gains, you end up giving up 15% of all the damage you would be doing during that period. Weapon skills, auto attacks, and oGCDs, as well as wasting the buff from Blood Weapon. And if you end up withholding your oGCDs for when you have Darkside back up again, that's even further losses, as you're essentially dead weight for that entire period where you're doing your crappy MP regen rotation.
Or you could just learn to properly manage your MP like every other DRK.I'm not going through full sets of rotations just to do this like you seem to think lol. You CAN leave Dark Side on while you're doing this, but it takes longer to refill your mp if you do. And all of this is assuming that blood price is on CD and, again, you just need a quick way to refill your mp.
No, it is a loss, and a very potent one at that. Even if you come up slightly on the positive side of MP gains after the Darkside reactivation cost, you are trading 15% of all the damage you do over that period for 120 extra potency in a single hit. Over the course of 2 Delirium combos (most damage and fastest way to regen MP), that's approximately 251 potency lost. And that's not even including oGCDs that you might throw in, and the most efficient use of Blood Weapon involves using as many oGCD physical attacks as possible. If you end up weaving in Plunge, Reprisal, and Low Blow, that's an additional 75 potency wasted. Should you choose not to use them when they become available, you're not helping your situation any further; and let's just hope you're not using C&S or Salted Earth. At minimum, you're looking at around 325 lost potency with your rotation, which might questionably earn you 120 back. The way you play your DRK strictly worse than every DRK out there, and you absolutely should not be giving any advice about the class to other players.P.S.S I take what I said back about it being a dps loss....because by recharging your mp up quickly this way, you're more able to recover lost dps by using multiple casted Dark Arts buffed attacks. If you don't like the way I play my Drk then that's totally fine with me. It works and I don't have any MP issues and my dps is solid so I've got no complaints. It's a fun job.