I actually take some issue with your damage estimation above, because you make one massive assumption which is not justified by the actual news articles. You assume that the doomsday event instantly killed 87% of all life; however, nowhere in the article does it say this. Rather, it just says that 87% of surface life will die, while listing other reasons for the extinction to occur: Notably, total planetary storms and vast sea level rises.
First, the SoE ships doing the first analysis arrive within a "few hours" of the incident. In the Cretaceous asteroid strike, the extinction took some time...weeks and months. In terms of extinction, within hours is close enough to "instantly".
Also, regarding the extinction, your statement is only true if you read only the first article. I made no such assumption, because the second article states that the
entire surface of the planet is incapable of supporting life. Not human life, life at all. That's a total extinction event. The article also states that the polar caps have been melted. To do that, you'd need to essentially boil the sea. Since it's EM damage, the article states that the surface of the planet has been "scorched".
Additionally, if we were to assume the values you come up with are accurate, then there would be secondary effects - notably, significant excavation of the crust directly beneath the detonation - which are nowhere described.
Again, it's EM damage. No crater necessary. The surface of the planet is scorched, not impacted. And, actually, this would resolve to more energy release than an asteroid impact, so my estimates of energy released are probably very low.
Even if this were not the case, this yield is not actually that spectacularly high. The Acclamator-class, for instance, had a main battery capable of firing a net yield of around 9.6 teratons with each barrage fired. It was also expected to survive similarly destructive inbound barrages; nonetheless, it was considered outdated and outmoded by the end of the Clone Wars. Its replacement, the Venator, has by some calculations an estimated peak weapons output of over 286 Teratons/sec, although this is admittedly a rough estimation.
First of all, that comes from the books, which Disney has declared non-canon. I used calculations based on the best case scenario (for the SW high-damage side) from the movies, where Star Destroyers were vaporizing asteroids. Why they seem so under-powered in other scenes, I don't know, but I was trying to give SW a giant benefit of the doubt.
Still, let's say we do take the SW extended universe as canon, and ignore all the books that portray SW weaponry as pea shooters. Even so...
A teraton is 1,000,000,000 tons of TNT. Let's assume that the Venator does 286 teratons every second. The Avatar doomsday, at the most conservative estimate, had to release the energy of
at least 200,000,000,000,000 tons of TNT. That is to say, 200,000 teratons. I stress that my estimate of the energy needed to scorch the surface of a planet, render it unfit for life, and melt polar caps, is woefully, incredibly on the conservative side. I could be low by orders of magnitude.
A Hawk frigate - fit with light missiles, not rockets, so less dps - will put out 880 teratons a second. A Raven battleship can put out 4,400 teratons a second. Even given your estimate, a couple of frigates from EvE are more powerful than a Venator class, while being much smaller.