While the Vampires and Wizards added a color in them for Commander that hadn't existed before, they weren't brand new directions for the tribes, just bringing together synergies that were already there
No need to create combos or elaborate plays when a card has the ability to double your tokens outright
Shes also a Human Warrior Ally, which is very synergistic for creature types
If a player is fortunate enough to activate Sarkhan's -8 ultimate ability, they are likely guaranteed victory, as Sarkhan allows its controller to search their deck for any number of Dragons, immediately putting them into play!
They get worse the more you have of them but in singleton this is fine
Some of the attacking creatures will probably be blocked and killed, but you can either let them die, or sacrifice the blocked ones and start benefiting from their abilities