I am pretty competent, and I only played unholy for fights where it made more sense until I came back from a four month break to find a guild that said unholy or bust. So those fights for me were Manny and Gorefiend(pre-recent guild). Granted I didn't get the vial of unending shadows until I came back recently. Simply because I didn't have the trinket that made unholy so much better than frost, and didn't care to practice that playstyle without it. NP unholy and frost were actually relatively comparable.