I rate
Blood Seeker
over
Pulse Tracker
. I don't really fancy a trigger that requires its owner to attack with a 1/1. It's fine for a deck built around giving creatures evasion, but I don't see Tracker as a reliable source of more than a couple of damage per opponent. Seeker doesn't have to put himself at risk and can be expected to do a lot more.
Chancellor of the Dross
is still strong as a late draw. It's not going to be an all-star in that situation, but it's still good and I don't think you'll be disappointed to draw it.
I don't think
No Mercy
or
Dread
are bad choices; they do have the problem Azureshade describes, but that only makes it ineffective against alpha strikes. There are more than enough occasions where having one of those out will deter
attacks of opportunity
intended to curb your gradual lifegain.
Finally, you could look at the upcoming Orzhov cards in Gatecrash (with the Extort mechanic). Whether there are any that will fit directly into this deck I don't know, but the mechanic suits. Oh, and you couldn't go wrong with a bit more removal to control the board.
Attrition
might suit, to go with
Bloodline Keeper
and
Blood Artist
. Or just more sweepers.
As for what to take out, the deck looks pretty strong overall.
Syphon Soul
would be my top choice, because I think it's a fairly redundant one-shot effect. It's strong, but I wouldn't fancy it unless I could use it multiple times. It doesn't affect the board, and you already have
Exsanguinate
to do the same thing, better. Second,
Lashwrithe
because I don't really see any urgent need to beef up creatures. I assume you're probably winning with
Bloodline Keeper
,
Malakir Bloodwitch
or
Exsanguinate
, and it doesn't greatly contribute to any of that. Finally,
Skirsdag High Priest
, because it really just looks like a weaker, harder-to-use
Bloodline Keeper
. You need to get spare creatures together, then wait for a Morbid trigger that doesn't also sweep those creatures. The deck's early game seems fine with twelve creatures who can be down by turn 3 (including all-star [c]Vampire Nighthawk), so I think you can safely switch him with something more expensive and less demanding.