DA+C@S

[Sleigh]

So let's assume that you are using souleater as your main combo (for the purpose of this example). You apply dark arts to souleater, adding 140 potency to the combo (400 instead of 260) and using carve and spit to gain around 900 mp (about half of using dark arts once). Your total potency is 900, while gaining 900 mp as well.

Instead, you decide to use dark arts on carve and spit during your combo. You add 350 potency to carve and spit (450 instead of 100), but lose the mp gain. Add to that your souleater combo, and you get a total potency of 1,110 and no mp gain.

So it all comes down to either getting 210 extra potency in your combo or 900 mp. Now, using dark arts on souleater gives you 140 bonus potency. You only gain half of a dark arts from using a standard carve and spit, meaning that 900 mp only adds up to a possible 70 potency (assuming you could half apply a dark arts to souleater). So the theoretical net gain of using dark arts on carve and spit is essentially 140 potency for every time that it is up.

In conclusion, you have a net loss of potency using carve and spit without dark arts, and this should really only be done when you are about to drop out of darkside (as the bonus 140 potency won't mean anything after you lose your 15% damage buff, even for just a few seconds).

It's even worse than this for C&S because you can replace any theoretically lost DA SE with a Delirium combo, taking the bonus potency down to 120.