Wyrms and Pegasi are strong but really, they aren't THAT strong and are extremely vulnerable to creature control and Paradox, Maxwell Demon's skill.
Dive is fine as is, and frankly Air deserves this. To make Dive effective with creatures that use it, you normally have to buff them anyways, and aside, they increase their attack at a highly expensive or off-element cost, which quickly leads to them being very inefficient compared to a Graboid's Evolve or Lava Golem's Growth.
As far as my testing goes, Dive is strong, especially in the upgraded environment, but it does not create any overpowered deck, and even with the cost of Shard of Readiness, you're probably better off just replacing them with Towers or using Shard of Readiness on a Nymph. Their vulnerability makes them horrible targets for Shards of Readiness, even if you get an efficient attack to cost ratio such as that of the Minor Phoenix.
Diving is one of the few niches Air has and to rewrite it would be to strip away one of the few strong points it currently has.
In Essence, don't touch it.