If your deck can support it then there is basically no reason not to include it however assessing when this is the case is trickier business
You have cards that make lots of Vampire tokens (like March of the Canonized, Mavren Fein, Charismatc Conqueror, and Sorin), cards that make Vampires bigger (like Legion Lieutenant, Etchings of the Chosen, and Radiant Destiny), as well as cards to keep your Vampires in play (like Timothar, Kindred Boon, and Dusk Legion Lieutenant)
Expect Secret Lair counterspells, Alchemy cards, and even counterspells from the infamously bonkers 'Un' Magic sets
When does the controller of Gleemax choose the target
This card shows that mana dorks that cost two mana usually tap for one mana on their own but offer some additional benefit