I don't think Koivu and Parise are markedly better (if at all) than Marleau and Thornton.
I think you'd be hard pressed to argue '12-'13 Koivu or Parise will be better than '10-'11 Marleau and Thorton, but I question whether the talent level of his line mates was the issue. It seemed that Heatley's issue in SJ was constantly playing hurt and not healing as much as an overall decline. If in fact his off-season knee proceedure helps his speed a bit, we may see a rejuvenated player in October.
When Heatley was on Atlanta and Ottawa he looked like one of the fastest guys out there, now he looks like one of the slowest players out there. I see 3rd liners pick his pockets all day. And you cant tell that he is dangling anymore because he has no speed to back it up. His dangles now are putting the puck under someones stick and instantly passing it. But please, dont let that take away from his amazing "sniping" ability. That guy can snipe.
But if he is put on the second line, He wont do too much better than last year.
I didn't see him much on Atlanta, but I never thought he was fast on Ottawa. The Heatley-Spezza-Alfredsson line always impressed me with their horizontal play in the offensive zone, a lot of weaving and setting up for great shots from the slot, as opposed to breaks down the wing with speed a la Kessel or Gaborik.