No it isn't. It's attack stat is 400, which is fully possible if you take an Adamant Salamence and 232 EV train it's attack stat. It also has a Life Orb which increases it's attack power a further 30%, plus Outrage has a base power of 120. Blissey's physical defenses are abysmal (10 base defense), it's Wall-ability comes in form of it's amount of HP. So Salamence didn't have to contend with any defense, it just had to blast away at Blissey's HP, with an attack stat of 520 after Life Orb is added. I'm guessing your Blissey had like between 550 - 714 in HP, well Salamence was able to eat away with a 520 attack stat and an attack with a base power of 120. It's completely logical why that would inflict so much damage. Against Skarmory it would not do that much damage as that has huge physical defenses and resistance to dragon type attacks, which is why Salamence is armed with Fire Blast.