I am writting this for my friend who asked me the same question. I reduced the number of heroes to minimum. He has:
Dark: Kunchen, Hannah,
Holy: Vivica(no costume), Sif, Kara, Faline
Ice: Magni with one costume, Finley with no costume
Nature: Lianna (no costume), Lady Locke, Elkanen with 2 costumes
Fire: Jean-Francois, Gravemaker (no costume), Ares
We play Dark Tank, so I was wondering about replacing one of nature or fire by second holy.
I look forward with your answers and sugestions.