Yup it's some kind of oversight by Blizzard in how Marrowgar checks for valid Bone Spike Targets. They have just never fixed it.What the hell, seriously? O.o
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I've done every boss of ICC 10 solo, with the exception of Dreamwalker for obvious reason. On Heroic 10 I've done everything other than Lich King and Dreamwalker. Everything other than Heroic Saurfang was done as Demonology with my pet's threat modifier off, just face tanking the bosses and burning them down. Heroic Saurfang was a slightly more challenging endeavor, lol. I hope that answers your question.
Soloing as a warlock.
Best chance of getting it done any time soon would be tanking the adds yourself with your pet tanking Nef. Again, if they're kited properly, they will deal very little damage and will fall over after 30 seconds. Obviously, its going to require more gear, but its not as impossible as you think.