For a 2v2 game, you heavily rely on your soul partner, and in 2v2 games I personally think sedna has way too much supporting power.
A sedna 1v1, which in a 2v2 game, happens a lot, cannot be pushed off her flag if she has mana simply put. In a 2v2 she can provide way too much support if she just has 1 partner, its rediculous.
I have no idea how GPG would ever fix this, but i personally think sedna heals too much, i think her auras should be buffed and her heals should be nerfed a little bit, thats how id fix it personally.