HTL + Dark Claw is an extremely common combo, Virizion is going to get taken out quickly whether you have an Eviolite or not. Unless you get it going T2, I don't think that'll work very well simply because it's so fragile (and that it requires Grass energy, which isn't commonly used).
Landorus EX is pretty much the only real "counter" to Darkrai, and even then, Darkrai can hold it's own. Landorus EX can theoretically do 90 damage to Darkrai with 1 energy and an HTL, which is devastating.
Landorus EX is pretty much the only real "counter" to Darkrai, and even then, Darkrai can hold it's own. Landorus EX can theoretically do 90 damage to Darkrai with 1 energy and an HTL, which is devastating.