Balancing the elemental dragons

Hi Riot, first off I thought the elemental dragons was a great idea for making the epic monster worth taking at any stage in the game however there seems to be a disparity in "worth" of the dragons. I think infernal is pretty balanced since the percents are nice and only scale so early infernals don't end games. The same really goes for Ocean dragon, except its more usful early than late, which i think is good balance. Mountain dragons seem to be a little too powerful, I saw an Azir & Rek'Sai take a tier 2 tower in 3 seconds late game with 2 mountains...seems a bit over tuned maybe drop a percent or two off (8/16/24)? For the Cloud dragon...well it just seems to be the dragon people take to get to the next one, kind of like a wrapper on a candy, I think if you adjusted the move speed to include a base increase and an out-of-combat move speed boost it would be more valued. Having extra move speed is great but is worthless (not really) if it doesn't help you fight, so adding a little extra base speed even in combat can make people really start to value all the dragons equally which I think was the goal to begin with right? Hopefully someone from Riot reads this and gives me some feed back :)