Besides having enough 2-drops (a necessity for EVERY deck), mana curve is tricky enough that it’s hard to nail down specific rules. Again, you need to be careful to differentiate between early drops and premium removal that you don’t really want to play turn 2. Eviscerate is great, but it’s not a 2 in the same way as River Crocolisk. There are also grey areas; Acidic Swamp Ooze is totally fine to play turn 2, but you’re even happier to play a different 2 first in case the other guy plays a weapon.