I disagree with the notion that Yetis are useless. I use Yetis in my build and have had good results. Reason:
- Sedna has low melee damage. Yetis increase your damage output dramatically.
- Sedna has no AOE damage. 4 Yetis aren't really AOE (until you get Wild Swings), but it does let you hit four additional targets at once.
- Distraction. They do fair amount of damage so they can distract enemie creeps/DGs while you sneak about.
- Escaping. When escaping, send Sedna off while letting your Yetis block pursuing DG. The poor pathfinding means enemy DG will waste valuble time walking around the Yetis. This is not to mention it's a huge distraction to the enemy DG.
- Tower destruction. Without Yetis, Sedna is abslutely useless against towers for much of the game. Yetis can quickly demolish a tower when backed up by priests and Sedna.
The way I play Sedna is I will send my army into the fray, while I hang just behind the skirmish line, dealing out heals as needed. And jumping in with a Pounce as the situation permits, usually to give chase for the death blow. I do very little damage by myself, and instead rely on my minions for damage. I played against a pure pounce/heal Sedna last night and never lost a single encounter while scoring several kills against her. It became apparent that when we both have the same levels in Pounce and Heal and my DPS way overpowers her, every encounter ends the same way. With my Yetis and a teammate's QoT's Uproot, we quickly pushed through their tower line and ended the game.
The downside is that I have to give up on Silence. It's a great skill, but most of the time I'm behind the skirmish line and thus don't have an opportunity to use it.