We already have Hestaby vs Lofwyr. Since that's a provable fact by observation (See also: Hestaby attacks S-K HQ in the middle east), and your math requires an Either/Or statement, it makes it resolve at 0.
However!
If you meant to say "What if the story becomes Hestaby vs Sirrug more than Hestaby vs Lofwyr", well, that's valid. The odds here are lower, simplydue to the status of the players in the conflict. To draw a parallel, let's grab Batman, because, hey, everybody likes Batman.
Now, you have a chance to see a long arc, say twelve issues, and entire year of publication, and you want a heavy hitting badguy to take the role opposite Batman. Clearly, your go-to guy is the Joker. It should be played out, but when people see Batman vs the Joker, they can't give you money fast enough.
But you think Joker's played out. You want to go with someone else, so you look through the list of Bat-Foes. Not Two-Face, not teh Riddler, not the Penguin, CLEARLy not Catwoman, not Mr Freeze ... the bench is deep, but he further down you do, the more obscure you get. Do you really want to do a 12 issue run of Batman vs Killer Croc, much less Batman vs the Penny Plunderer? Now, I'm not saying you can't make an epic tale of PP wanting to get his greatest treasure back from teh Batcave, but, it's gonna be awful hard to pitch to the editor and when people see it on a store shelf, they go, "Oh cool! Batman against ... The Penny Plunderer? Who the heck is that? Stupid comics, I want the Joker!"
It's not to say that it can't be done, of course. The Long Halloween gives us Hangman, a new character just for that arc. Knightful introduced Bane, while the Demon's Head introduced Ra's al Ghoul. Note that these are iontroduced a new guy, rather than dug a C-lister and put them on the front line? There's a reason for that.
Hestaby vs Lofwyr is where battle lines are drawn. That's the main event. If you were told that you were getting Hulk Hogan vs the Ultimate Warrior, but instead got Hulk Hogan vs Barry Horowitz, would you be happy? Probably not.
Sirrug's story and Hestaby's got linked as soon as she came out on national... heck ... INTERNATIONAL TV and called him out. What this really did is tell the dragons of teh world, in no uncertain terms, that the Old Ways no longer applied, that she was willing to put dragons under the rule of squishy little short-lived blips. That's teh part that doesn't sit well with the old guard, and that's why battle lines are being drawn. No one's stepping up to defend Sirrug you might notice, they're lining up to defend the old ways and combat *Hestaby*. Even she isn't directly going after Sirrug, so much as saying "Hey mortal authorities, you have my permission to go arrest him. Uhm. Good luck with that, I'll be over here."
TL; DR: Sirrug was the fuse, Lofwyr's the explosion.
