Oak can't get Staff of Renewel.
Sedna gets stronger with a longer cooldown time: Magnificent Presence.
Even with a 90 second cooldown:
90 * (1 - .15 - .15 - .17) == 47.7 seconds. Sedna can virtual perma-lock all by herself, and Silence gives her the tools to guarentee a lock (even 3 seconds), but would probably result in her dying. Solution: Oak + Sedna. Now we can permalock on a 48 second timer, shielded, at level 15 (assuming we have your Celerity flag).I would hate to see a UB, Oak, Sedna (UB with Staff of Renewel) the only viable 3v3 team because of their ability to lock down portals infintely.
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Oak can do something only ONE demigod can do right now, and that's waltz up to a portal as a cap lock expires, shield, lock, and teleport to safety when three enemies are standing there. That's a totally unique Oak ability that would be removed with a 3 second cap lock cast, and it would be a much, much bigger loss than you acknowledge."
I acknowledged that his ability to do so is removed, however, I'm focusing on the fact that everyother demigod except Sedna would be greviously affected. Oak is still able to do the essential action: locking the portal. Although his safety is far from guarenteed with a 3 second cast, LOCKING THE PORTAL WINS GAMES. Plus, (more than) half the time the Oak is porting TO the lock flag, locking, and then running, sometimes with Wand of Speed.
... so? I think that's a great thing. Any decent Oak will do this. It's no different than a Regulus shooting out of range of towers or a Rook hiding behind his tower farm. It's one of the flavors of the demigod and something that you really need to take into account when playing against an Oak.
"...adding more strategy/tactics into the game."
Actually, taking a lot away. Holding an enemy portal becomes much, much less viable of a strategy with a 3 second lock. The only way to win against an equally matched is a slow and steady push into the Valor flag. Which you won't be able to lock either. So... yeah it's going to be a slow, slow death as you buy lots of artifacts (Deathbringer's Silence anyone?).