I personally like as much variation as possible though. There should be consequences for our actions. Infact, to me it feels wrong giving the Dawnguard a chance at becoming a Vampire Lord. Then again, just my opinion
Personally I think it makes sense in the circomstances, but I agree that the anti-undead spells are best when they are Dawnguard exclusive(they're not, you can still get them by calming the folks who sell them), like the Heal Undead spells are good as vampire only spells.
One option I wish we got was to kill Serana. Not because I have anyhitng against her, but because it would make sense as a vampire hunter to at least get the option.