Hot take: Worst thing about MCOC (probably not what you're thinking)
No it's not any of the many things other people and myself have complained about in the past. It's the fact that you cannot consistently get your 2* roster complete with basic-pool hero's. Not even if you throw money/units at it.
The thing that stings the most is the fact that it is possible with 3* and 4* in arena to even 5* since you can get those with the monthly quests.
I am a collector and a completionist. That's the biggest reason I started this game in the first place. I have grinded arena and monthly quests to get my roster as complete as possible.
What do you think, should there be a arena/quest you can earn them or should 2* basic pools be in the PHCs for example?