Are dragon spawns really random?

Solution 1:

As said here by Meddler:

Instead of the current 5-buff dragon system, we’re changing it to 4 different types of elemental dragons, each of which gives a different buff. The types and order of elemental dragon spawn are randomized (with some restrictions) and it’s possible to get multiple stacks of one element (e.g. 2 air dragon kills gives more movement speed than 1 air dragon kill). After 35 minutes, the dragons are replaced by an elder dragon, who gives a consistent buff of his own and amplifies existing buffs when killed.

The only restrictions are:

1. There are never more than 3 different elemental dragons in a match (so if you get 1 fire, 1 mountain, 1 cloud, the 4th dragon will be one of those again and there won't be any water in that match).

2. A given elemental dragon will never appear more than 3 times in 1 match (so you'll never get 4 fire dragons in the same match)

                                                             -GeneralMike
   

Edit: Here is a Reddit post where someone killed 100 dragons and kept tabs on what types they were and more. Perhaps this is more like what you seek.