I can't see you doing 15k DPS as Unholy on the old realms unless you're BiS or near-BiS. And why tf do you have 1/3 Reaping, in case you could've spent it on Unholy Blight - a 10% increase on Death Coil for just one TP. Even more so when you have Dirge, which works towards higher Death Coil count.
This is pretty much the best Unholy build for end-game. Wandering Plague does as much DPS on single-target as Blood-Caked Blade and does significant damage on multi-target. Unholy Blight I already explained - 10% increase on Death Coil for 1 talent point, pure no-brainer. Between Morbidity and Dirge, the first one nets more DPS - it increases your DC by further 10% and reduces your main AoE ability's cooldown, whereas Dirge only works towards higher RP for more DCs - something you're not focusing on at end-game because at that point Scourge Strike is your main damage. 3/3 Reaping is also a no-brainer - it gives you an extra Scourge Strike in every other rune cycle.