No shit, try to want middle potions, and you'll be happy. But you must mean it! 

I'm currently doing "mix 10 superior potions" missions, so I need 100 middles. They never drop as far as my brain tells me.

That's just RNG for you, my guy. Sometimes we get nothing, sometimes we get lucky. 

Lxzy said:

That's just RNG for you, my guy. Sometimes we get nothing, sometimes we get lucky. 

Also why not do Stage 15 though?

Because Stage 14 is stil safe for me to beat the level.

I also don't think that stage 14 or 15 makes a big difference. Runnig Level 14 should bring much bigger awards as those given above.

when I am grinding pots I do the max lvl dungeon and drag along two heros I need to lvl up with xp while playing a XP token

That way I get to level up some champions while I grind  pots.

Accept it. Do stage 15 and think like each battle give you = 1 greater potion. 

Accept it. Do stage 15 and think like each battle give you = 1 greater potion. 

At end-game, 20 runs is nothing, I collected too many potions, 2 days ago was the 1st time I re-do potion dungeon after 6 months. It would be great if Plarium release potion tournament/event. 

You only need RNG when you farm small amount of potions, it's called Luck or Bad luck. If you farm 10000s times, it end up Average number.