I suspect its mostly due to the very easy poison counter wins Atraxa can pull off, but really, does she deserve the hate
The static ability to double all damage Wolverine deals includes commander damage, meaning if it deals 11 combat damage, that will be doubled into 22 and be able to take someone out fully through commander damage
You can cast popular 2-drop Selesnya commanders like Sythis, Harvest's Hand and Catti-brie of Mithral Hall as long as you have Savannah and a Mox Emerald or Mox Pearl in your opening hand
Rings of Brighthearth Rings of Brighthearth doubles up loyalty abilities for just 2 mana
Inti's effect to discard for a +1/+1 counter on an attacking creature triggers off of any attack, not just its own
These wells are an important resource - if you play cleverly, you can starve your opponent of the points they need to defend themselves before going in for the kill