I'm not sure how "We either all six die, or most of us die, or we fuck up the entire planet. So we'll back up and sit this one out." = being selfish dicks..
Oh it's easy really. Sacrificing yourself to save millions of lives = selfless. Sacrificing millions of lives to save yourself = selfish. Pretty straightforward.
But in this case it'd literally be "Sacrifice myself to die, then empower the beast that killed me so it can much more easily go and wipe out nations."
There is no saving in this context. It's "Kill a dragon/most or all of the dragons and ruin Tyria, even if it's just the local regions humanity has spread to if it's not globally" or "Die, have all my magic absorbed into a beast that feeds and grows more powerful directly off magic consumption so it can kill all those humans."
Selfish in a certain context, perhaps. But it's not a dick move to back out of this conflict. Especially with the conditions. edit: Sure, they probably could've handled some things better, but if the garden of the gods book is true for the most part, they are trying to find a new place for humanity .