Woppin: Nobody cares about the side effects of being double hammer slammed, because it's never going to happen. Even if I were to somehow have absolutely perfect timing between both Rooks, and anything less would result in just one Slam, the other Sedna can easily heal you, Pounce one rook, or both to save you, assuming you weren't silly enough to stand in a line. On the contrary, it's easy to spam pounce till the dogs come home. Moreover, if there's two sednas and two rooks, they can both Pounce one Rook, but two Rooks can't roll one Sedna. Or rather, you could roll two Sednas, but the co-ordination to do that is off the charts compared to that required to double Pounce.
Pounce and Heal scale absolutely. If there's two Sednas, Pounce becomes doubly as effective as one Sedna, and Heal even more so. Hammer Slam and Boulder Roll cannot ever possibly achieve that in practice, and even if they did, double heal would heal up the damage extremely quickly.
As for low damage, perhaps you haven't played against any decent Sednas, but most of them will stack Bishops and Siege Archers. Sedna may be no Rook in terms of DPS, but she's impossible to kill when your Roll and Hammer Slam does only 400 damage after she Heals herself, and then Pounce is 1000 to you.
As for quick consumables, a 750HP pot vs 1000 damage pounce or 800 pentinence. Yeah, that's good stuff right there.
UB and Rook are fighting. UB Spits Rook. Then, when Rook is casting Hammer Slam, UB uses Foul Grasp and Interrupts him. Rook gets facepwned. Alternatively, UB can just Grasp Rook at any time and then run away from the Hammer Slam that he knows is coming, and Rook gets fucked over.
Yes, Hammer Slam does a lot of damage. But after that's gone off, Rook sucks, unless you want me to spend an entire minute+ preparing a tower farm beforehand and hoping the enemy team will fight there, and if it gets interrupted, he's got nothing. So if your enemy stacks more than 3k health, you're fucked, and it absolutely does not scale in team games compared to how well other abilities do.