The Ocean Drake is Too Strong
IMO, the new Elemental Dragons are unbalanced. The Ocean Drake provides a huge amount of sustain for the entire team that can practically win a game if a team picks up one or two very early. The Inferno Drake, on the other hand, scales really well, a team with 3 inferno drakes straight up wins the game late against a team with none.
The Cloud Drake, however, doesn't seem to do much, as you only get around 10 movespeed each if you already have boots 2+ another movespeed item. The Mountain Drake doesn't help you much unless you are already winning.
Riot should nerf the Ocean Drakes, for the early game at least, and the Inferno Drakes (I'd say go to 6% bonus AD/AP like the old 1st Dragon instead of 8%). I'd suggest buffing or changing Cloud Drake's buff, and changing Mountain Drakes buff. I'd suggest giving extra damage to minions/regular jungle monsters as well for mountain drake. I'm not sure what to do for Cloud Drake, but making it a % boost or allowing it to work in combat might work.