I haven't played my deathknight in a long long time, but the only thing I'd suggest is a few upgrades for gear. Get some blues/purples in there and you should be fine.
I'm sure my vague answer won't be much help, but as far as I can see you should be good with that spec. I'd suggest, perhaps, a point OUT of Might of Morgraine and putting it in Sudden Doom. I like the free death coil, personally, but the extra crit is always good.
My friend's a DK Blood tank and he solo's crap all the time. He has a video of him soloing Doomwalker, the level 70 world boss. I was there when he did it, I bet him my shield DE that he couldn't do it. Come to find out, he could. :[
He said he was having constant heals... honestly I'm not sure what he was doing, but I did know he was healing himself, as seen on the video, 1ks, 7ks at a time. But this was against a level 70 raid boss.
You could definitely solo the easier stuff, any of 60 stuff (maybe not AQ40), and maybe some 70 heroics too, if you're careful. The guy I did link was in high end gear, so it's kinda hard to say so or not. But it seems DKs can solo a lot of stuff though. ;]