Sedna's Pounce is formidable if she ever makes it to higher levels, though it does have the weakness of being a very close range skill. However, it *DOES* interrupt enemy demigods (Meaning you can stop a Hammer Slam dead in its tracks) and it has a very, VERY short cooldown timer if you own a Celerity Flag and max out Magnificent Presence.
Because of its major weakness (Again, the Range), I have one suggestion: Give Pounce a larger cast range, allowing Sedna to target a demigod up to (~15?) yards away, then having the cat charge at the target and pounce it for the damage, working similarly to Charge from Diablo 2. This would allow her to overcome her weakness against ranged demigods as well as giving Pounce a little more flavor.
Currently, Sedna's only real weakness is an Ice Torchbearer's strength. His stuns and Deep Freeze. He is very capable of stopping her in her tracks and reducing her pounce speed to an abysmal level. Because of the short length of her Silence, she can't keep him from starting his combo well enough. (For reference, reducing Silence with Maxed Magnificent Presence, a Stormbringer, and both Celerity Flags on Cataract... the cooldown timer on Silence is 12 seconds...and that's an IDEAL situation, not a realistic one. If you manage this, Heal is 4-5 seconds and Pounce is 3 seconds.) The only advantage she has against an Ice TB is that she can (generally) survive his combo, but even then, it's just barely... and if he has ANY teammates, you WILL be dead.