Here's a list of things I notice off the bat. Don't expect any kind of coherence
In my experience so far in playing a DK, you never need to fill more than 3 points in Desecration to keep the buff up in any non-solo situation. Two seems lacklustre and five is overkill.
You don't 'need' Outbreak, it feels like wasted points but I guess if you really want bigger Plague Strikes its nice enough.
You definitley DO need Virulence, I'd pretty much say it's essential in any PVE unholy build. Nothing's worse than something missing.
I think you're over-valuing Dark Conviction. Looking at it from a warrior perspective, we used Cruelty because it's easily within reach. DC on the other hand is quite deep and while its always nice to have extra crit, couldn't the points be better used in something else? Improved Icy Touch, for example, is nice if you don't have a warrior/bear/protadin providing a slow and always good for instances.