Which faction poses the greatest challenge for the Dwarves?

...The game was made by professionals and they did a very good job. I'm not arguing that there are some imbalances, but only in certain stages. If you don't believe me...

It's well said that the imbalance only exists in certain stages...
and in the next post, you mentioned the possibility of rushing with Necromancer against Gnomes...aren't those the imbalances?! The problem with Gnomes is that they rarely survive a rush.