Given that, by putting the Lord on a Dragon means that you have to get into combat (it is tying up 3/4 of your character slots and more than 1/3 of your points at 2k). I would say therefore either von Carstein or Blood Dragon. Bearing in mind that you have 2 characters only, vC gives the extra magic dice, BD is the better combatant and comes with Plate Armour.
I would look at your likely opponents and go from there.
Well, being one of the vampministrators I have to remain nice and impartial Skaramak
The thing about the wraith is I could imagine it being a real nasty character hunter if equipped right (the obsidian amulet) so that it could become an avatar of death for characters and unit champions alike. Its leadership is also akin to that of a Vampire Thrall but it causes terror.
I personly take a blood dragon lord with a Great Weapon, red fury, heart piercing, master strike, strength of steal necro with book of arkhan and a scroll necro with a power fimilier
this gives me 9 power dice that i can distribute evenly between my characters as well as 7 dispel dice and a bound item, not to mention a vamp who can give anything a good slap in combat.
iv experimented with a wraith and found that if put in a unit of dire wolves ( you only need about 5 of them) and equipped with the talon of death he can take out any war machine crew that u come up against even dwarfs wil be hard pressed.
My prefared set of characters for a basic VC army goes like this:
Von carstaine count gw, ring of the night, staff of damination, aura of dark majesty, lv2
Von carstaine thrall gw, flayed hauberk, wolf form
Necromancer lv2, black periapt, scroll
Necromancer lv2, scroll, book of arkhan
this is probebly one of the best sets of charcters for a balanced tourny army you can use, mostly since it gives you tools to deal with chariots (something that is normaly hard to deal with when you play VC)
i am still however debating with myslef if the count really need the ring, since t5 and healing normaly keeps him alive anyway, and so far its only dancemans slayer musician that have killed my carstine count.....maybe walking death would benefit him more
prefared Necrach line up:
Necrach Count.......when i feel for it; on a winged nightmare lvl2(3), NNB, ring of the night, book of arkhan
Necrach Thrall BSB, NNB
Necromancer lvl2, scroll, black periapt
Wight Lord Lance, barded steed, heavy armour, shield, cursed book
this one may seam a bit odd to most of you i presume, but i have found that a lord for Necrach is not worth it, since NNB mostly make the lord unessesary and you can spread out your fighting power more with one more hero slot.
with the other bloodlines i would might consider a lord.....but i have not played any of them mutch yet in order to have some form of prefered character line up
Yeah I know this setup is not very original but nevertheless, it is a "copy" of my setup from 5th edition, of course adjusted to 6th edition rules when it hit the shelves all those years ago . It still works with 7th (I'm looking forward to the new VC book!).