There's no real rotation for drk tbh. I typically will use DA directly prior to the buffed attack, rather than at the start, due to the fact that if I'm at full hp, I'm not going to buff my SE, I'll just throw in a delirium instead generally. Throughout the fight, I'll toss in unmend occasionally to substitute for an attack to get some time to regen tp. For an opener, I generally go Unmend, Plunge (I macro'd plunge into unmend to make this ever so slightly faster), Blood Price, Scourge, Dark Arts, Heavy Slash, Salted Earth, Spinning Slash, Low Blow, Power Slash, Carve and Spit. From there, depending on dps, I'll either drop grit then, or do one more buffed power slash, then drop grit.

AoE, DA, Blood Price, Unmend one target, plunge into another, drop salted earth, dark passenger, Shadowskin after DP wears off, Abyss spam, buffed with DA when possible, Carve and Spit when needed, Reprisal/Plunge weaved on CD, DA+DD when Shadowskin falls off.