Since it seems like they actually look at the forums id like to suggest that Purple heroes become viable for more than Exp fodder. Lets actually give them a use again for higher level players.
The reason they are rare heroes and not epic heroes is due to the fact how they are obtained.
Just to be clear, I have used 1 of these heroes for my layout in battle royale for quite some time before she became obsolete. Shining Wizard. Her aid adds more mercenaries. And that was the real deal back then. But she has been long useful to me in this mode, so in my opinion, she is good enough as she is.