"then Thrall stole our kill"

I think this is really the root of the problem. Deathwing was never meant to be something we mortals could kill. That's the entire POINT of the way the two fights unfold. Deathwing is just plain too much for us. We can NOT do it alone. Thrall can't steal "our kill" because WE can't kill Deathwing. He's just too powerful.

The design of the fight was supposed to emphasize this point, but it obviously failed in some respects. The point is that you can't stand toe-to-toe with Deathwing. We can barely take out his foot WITH help from the Aspects. Taking out the whole dragon with just your raid isn't going to happen.

The problem is that Deathwing's immense power, apparently, hasn't been shown clearly enough. Random roasting of zones was a good idea, but it's too remote and unattached. Though it's too late, here's my idea. After killing Ultraxion, before Thrall can use the Dragon Soul, Deathwing should have attacked us. He could have been all pissed that we killed Ultraxion and flown up to take his place. While he's chattering about how mad he is, he would be an attackable mob, though he wouldn't attack back. He'd have a buff called "Elementium Plating" which reduces all damage he takes to 1. It might even prevent debuffs like Hunter's Mark or Sunder Armor from being applied.

So here the raid would be wailing on Deathwing and doing nothing. He'd finish his speech, laugh and swipe at the tank. BOOM, dead tank. That swipe would not only one-shot the tank, but it would cleave and kill anyone in melee range, maybe even the ranged. If not, he breathes fire and wipes out anyone left alive, except the Aspects in their bubble. This is the point Thrall uses the Dragon Soul and the cinematic shows up. Deathwing tries to dodge, takes a hit, blows up a gunship and flees, just like now. Except we're all dead. We faced down the Destroyer and were killed like the gnats we are. Alexstrasza rezzes us (similar to Terenas in the LK fight), thanks us for the help and apologizes that they must ask more of us.

Here's where we show the heroes we are. Even though we just got rocked by the Destroyer, even though no one would blame us if we backed out after that, we hop on the Gunship and go anyway. I think this would have offered a better context to the whole Spine/Madness fight. It helps the players directly understand how powerful Deathwing is: We tried and couldn't even dent him and then he wiped us out. The only reason we have a shot later is because the Dragon Soul did the damage and gave us the opening. Even then we still need power from the Aspects. Yet they couldn't do it without us. Despite just being crushed, we get back up and won't give in. That's what makes it Heroic, that we refuse to back down in the face of true despair.

I think that's what's really been missing all expansion. A true understanding of just how powerful and unstoppable Deathwing really is. The feeling you got from the Lich King in HoR as you did everything you could to escape, but it (almost) wasn't enough. Deathwing's random torching was cool, but it didn't give you that real feel of despair and powerlessness. The idea behind Madness is good, it just wasn't fleshed out well enough pre-fight.