Well, I think it requires a separate article from my previous lengthy Sed+QoT write-up. The changes are quite significant this time. Basically, three factors have influenced my decision to change the build: (1) accumulating some 2v2 experience; (2) seeing Nastyblade's MCP/Speed Sedna in action and analyzing his build; (3) Hedgie's remark in one of my threads concerning Pounce wasting its full potential, unless you max out IG or go Cloak-Pounce.
That's how I play Sedna now:
Favor: BotF
1. Heal 1
2. HW 1
3. IG 1
4. Pounce 1
5. HW 2
6. Pounce 2
7. Pounce 3
8. Silence 1 or Counter Healing (depending on number of enemy generals and their healer idols rank)
9. Heal 2 or Silence 1
10. Pounce 4
11. Heal 3 or Heal 2
12. IG 2 or Heal 3
13. IG 3 or IG 2
14. Silence 2 or IG 3
15. Silence 3 or Silence 2
16. MP 1 or Silence 3
17. MP 2 or MP 1
18. MP 3 or MP 2
19. Heal 4 or MP 3
20. Life's Child or Heal 4
Gear:
0. Monks
1. Banded
2. Boots of Speed
3. Unbreakables
4. Monks -> Bishops/High Priests/Clerics (depending on number of allied generals)
5. Nimoth Chest
6. Hauberk
7. Boots of Speed -> Vlemish
8. Banded -> J-Treads
9. Nimoth -> Girdle of Giants
Justification:
I've found empirically that having +15% speed at 6-10, when Pounce is at its strongest and can take off 20-25% of enemy DG's hp bar, is crucial while chasing or sneaking to get that final Pounce on a surprised ranged attacker. Boots of Speed also increase Sedna's survivability more than another armor and make monk-managing significanly more efficient (a passive bonus to minion movement speed). After 10, there is usually a short period where I run without BoS, since I need one helm to use Silence in mid-game battles. This period is usually very short for me. Later-mid game I sell Banded for J-Treads, and invest 2 additional skill points into IG. I've learnt the hard way J-Treads increase both Sed's survivability and efficiency later game much more than any non-artifact pure hp/armor item could. I don't get Siege Demolishers with Sed, unless swimming in gold, as I feel they have a somewhat poor synergy with her.
Replays of skilled matches where this build is demonstrated (hopefully, I'll get better examples, but that'll do for now):
http://www.jeeplays.com/replay/details/1/12
http://www.jeeplays.com/replay/details/1/13
http://www.jeeplays.com/replay/details/1/14
http://www.jeeplays.com/replay/details/1/20