That has a certain logic to it.
Rare right now is set up so that each item rolls between 1 and 100 basically. So 1 is the rarest option and 100 is quite common. Rare can roll 0-1 and common can roll 0-100. Not my favorite way to do it, but it works for this game.
If a rarity = 1 item was only 25% better than a rarity = 50 item, which is only 25% better than a rarity = 100 item, we would have a pretty good balance. Randomness would give you a margin of 25% quality. Not going to break the game, but still making loot exciting. Endgame items that are 100% to 200% better, the ultra rares, should not be in the random pool. They should be unlocked from quests. Hopefully quests will get expounded upon so that this will blend into a player's specialization in the game, but we will just have to see.
I have already posted at length on traits and randomness, but suffice to say, I think there should be a balance between randomness and class specialization.