Both of those builds seem ridiculous to me. But, before I get to that, I'll comment on the initial question.
If you are Unholy, you are using SS.
For one, you seem to misunderstand Oblit. It doesn't consume one disease, it consumes ALL of them.
Second of all, using Oblit but going deep Unholy means that: A. you never get any skills that boost Oblit damage, and those that exist in the Unholy tree to boost SS damage are useless.
Third of all, you seem to not realize that Unholy is our best AoE tanking tree.
About your build:
Virulence: Unnecessary as a tank. 3% isn't worth it for 3 points. It'll only help IT, really, and DCs when you are tanking a boss. And, with epidemic, missing the former doesn't matter because you won't run out the clock. And, with the SS glyph, you will usually find yourself refreshing diseases without spells.
OaPH: NO. It is UNACCEPTABLE to pass up some AWESOME talents, but take this. 100% not okay. It will not help you be a better tank. Well, 20% reduction to stun and fear is nice in some encounters, but those are few and far between (those where it actually matters).
No UB: WHY? With the Glyph, that is 30 seconds of easy threat. Phenomenal in AoE. Good on bosses (it should do more than DC on a boss, if I recall, as Unholy). No reason to pass this up.
No Impurity: UB + Impurity = Joy. DnD, too, but I don't use that often. It'll also boost your IT, your DC, your disease damage, your AMZ absorbancy, your CE (if you take it) and your Garg (if you take it). Should grab it as a PvE DK.
No Dirge: While these two points won't make or break you, more RP = more RSs = more threat and DpS.
NotD and Perma-Pet: While you CAN take these, it is generally considered a waste. Some DKs will take NotD to lower the AotD CD to 10 minutes, because it is also a mitigation technique. Your pet will often die quickly, too, without GF (which is not worth it as a tank). Your ghouls won't give you threat, either.
Desecration: A matter of preference. I don't take it, because too many fights are mobile and it lowers my FpS for too small an effect. But, the fact that SS causes it too, now, makes it better.
No WP: WHY? This talent is AWESOME. And it gets exponentially better as you add targets. Even on bosses it is a nice boost (generally another 100-300 damage every 15 seconds, boosted by your EP).
Garg: You get fewer RSs for an ability that won't give you any threat. On top of that, you don't take Impurity, which is a noticeable DpS increase for it.
No Bladed Armor: WHY? WHY, WHY, WHY? This skill is phenomenal, ESPECIALLY for Unholy DKs.
No Two-Handed Weapon Specialization: 4% more damage for all your SSs, PSs, RSs, and auto-attacks.
Black Ice: It is... okay. But, I have NO CLUE why you are taking it in that build. The only thing it will do for you is boost your DCs and your weapon component of SS by 10%. Not that great for 5 points, considering what you lose elsewhere.
Imp Icy Touch: A nice mitigation talent, but you shouldn't take it if you are already passing up better things.
Try this build. There are two floater points you can put elsewhere. If you place them in anything before Bone Shield's tier, you can lose CE. For that matter, you can move CE's point wherever you want it.
Rotation for Single Targets:
IT>PS>SS>BS>BS>UB>SS>SS>SS>DC, repeat. If your SS glyph procs, replace the IT>PS with a SS. Replace UBs with DCs until the rotation is up (It will likely be at the end of your first repeat. Use RS whenever possible, but try and budget for UB. You can skip DCs for two RSs, if you'd like (rather, if you don't have enough RP for DC, that's fine).
Rotation for Multiple Targets:
IT>PS>Pest>BB>SS>UB>SS>SS>BB>BB>DC>repeat. Make sure your diseases are always up on all mobs--Wandering Plague will work wonders. And the fact that always having BP up is good for your UB damage.
You can use DnD if you'd like. Just make it DnD>PS>IT>BB>UB>SS>SS>BB>BB>DC, repeat (it can mix up a bit, because DnD refreshes 3 runes at once).