I like playing with Minion builds. Yetis are not the best of the bunch, but they can be powerful, especially as Sedna has a lot of minion buffs.
However, this build is really situational. I always play assasin first, get Heal (600Hp emergency), then either healing winds, Inner Grace and pounce (for interrupt). By then you should be able to see what your opponents are doing. If you then go minion build stick to minion skills, no more heal or pounce.
Reg and UB and the ones you are watching for. If they are going AoE builds, then minions are not a good idea. If they are going spit or snipe builds, then carry on.
If you are fighting TB, then don't even bother with a minion build, they are the ultimate counter.
If you are fighting a Tower Rook, then minion build rocks, the towers effectiveness is greatly reduced as there so many targets.
The great thing about minion build Sedna is that it is relatively mana light, this means you can go for a lot more armour and HP. You will be very hard to shift from a lane, just don't expect too many kills.