i run a similar deck ( probably copy of mine) always ran into mana problem and i ran 22 swarm in the beginning
far from the best aggro deck out there especially legacy (
dark ritual help but only for one turn)that's why i run
liliana of the dark realms( turn 2
dark ritual - liliana thin out ur deck, extra damage, higher chance of drawing another spell)
it's hard to get 5 vampire out on the field especially when u r trading creature
Malakir Bloodwitch not a good card grey merchant of asphodel is way better but not vampire
Whip of Erebosis good but i never cast it once. cuz i have better spell to cast for 4 mana(that's almost skiping a turn)
u have no way of returning creature from the graveyard board wipe = gg
i recently added
vampire hexmage with 1st strike u can be very aggro in the beginning
i run
Kalastria Highborn and
Bloodghast to make my opponent
think twice before trading creature with me. making it easier to get 5 vampire out with liliana
Bloodghast always come back
Guul Draz Assassin is great for mid to late game picking off weak monster(blocker)
Erebos, God of the Dead for card draw is not bad