I am not making excuses, just stating commentary and speculating based on what was in print.
Thor lost this fight cause Tutinax is an absolute BEAST!!!!!! He is the physically most powerful Deviant there is, capable of killing multiple eternals at once. How many opponents can withstand Thors hammer shots the way Tutinax did and tell Thor that his limbs are more powerful than his and his weak mallet. No reason for an excuse losing a round to this monster does Thor no injustice at all. Hell Thor put up a hell of a fight and although he lost the fight he didn't look like he was close to death which says alot about his durability.