Death Knight Tier 13 Set Bonuses

Death Knight Tier 13 bonuses, as published by WoW Joystick (or whatever that blog’s name is now):

• Blood, 2P — When an attack drops your health below 35%, one of your Blood Runes will immediately activate and convert into a Death Rune for the next 20 sec. This effect cannot occur more than once every 45 sec.
• Blood, 4P — Your Vampiric Blood ability also affects all party and raid members for 50% of the effect it has on you.
• DPS, 2P — Sudden Doom has a 30% chance and Rime has a 60% chance to grant 2 charges when triggered instead of 1.
• DPS, 4P — Runic Empowerment has a 25% chance and Runic Corruption has a 40% chance to also grant 710 mastery rating for 12 sec when activated.

Overall this looks interesting, and subject to so many smaller factors like up-time and usage that I can’t see any of these as great overall; useful, but not great.
The bonuses also seem somewhat different to some of the other class bonuses in the tier 13. Priests and Hunters specifically seem to have a direct damage increase here, and although I hate to be doing cross class comparison (as its often not at all valid), it does seem odd.
As a breakdown consider:
Tank 2P sounds useful. Being rune locked and at low health is a bitch sometimes, and it may also help for those DKs (like myself) that get out of sync in the rune usage. I am not sure if it will be a great enhancer for the endgame raiders who don’t make smaller mistakes, or if the use of a blood + other rune might cause the same type of switch-up in the rune cooldowns? It certainly sounds reasonable though to assist when health is sub 35% and you need that health bump while a large heal is being cast.
Tank 4P is it good enough to be worth it for the raid? I’m not not sure. Vampiric Blood reads as: “Temporarily grants the Death Knight 15% of maximum health and increases the amount of health received from healing spells and effects by 25% for 10 sec. After the effect expires, the health is lost.“
I don’t think of Vampiric Blood as a raid saver, and I see it to save my own skin, not that of the raid. Why have a set bonus, especially a 4pc bonus that has no direct additional benefit to the DK? Sure, the raid might live slightly longer in an AoE fight, but we’re using VB because we’re getting slammed rather than the raid this bonus means nothing. A direct boost, or some ability that was always on would be better.
Dps 2P bonus is useful. At a first glance it reads as if there will be additional free of our abilities that consume no resources, like getting Rime or Sudden Doom twice in a row. But I’m not sure if that is what is meant, as I find that “tooltip” description unclear. Resource free strikes are great. The affect on rotations should be easy to absorb, and it certainly sounds like Frost at least will become even more of a straight Obliterate spec.
Dps 4P will be dependand on the proc rate (how often it goes off). Mastery is very nice and useful for both Unholy and Frost playstyles, and having more for free is good. It may also change the stat weightings for us once we have the four piece bonus, as Mastery might become really darn useful. The EJ forums seem to indicate that the 2P + 4P bonuses might change the stat weighting a little away from Haste and toward Mastery, but this is yet to be math’ed out.
Personally I doubt I’ll see either of the 4p bonuses on my DK, so the 2P bonuses are probably more important to me. I do like the fact that the set bonuses can be tweaked and altered as time passes, so perhaps even if these are a little lackluster now, they can be buffed without smashing the rest of the game altogether.
Ps. I’d also like to see the cosmetic armor model too. It will not make a single sod of difference as far as the mechanics go, but I like to have two reasons to strive for the Tier sets; stats alone are enough – but a good armour set is such a wonderful motivator.  I’m sick to death of the non-tier shoulders I have now in both Tank and Dps sets.