Oro was planning to destroy Konoha. That was the point of attacking it, and he explicitly said it many times. Isolating the highest commanding officer and decapitating the head of an organization is a viable (and much used) military tactic (ref: Osama bin Ladin). Though yes, killing Hiruzen was one of his objectives. However, even when the operation started, Sasuke was left by himself and wasn't approached by anyone. Sasuke himself was the one who chased after Gaara (and indeed, it was only some time after that Sasuke was tempted to go and seek out Orochimaru). So retrieving Sasuke was not one of the objectives of the battle.
Ok, lets list the objectives in this battle:
Neutralize Orochimaru as a threat to Konoha.
Oro achieved Secondary Objective, but failed on his Primary. Hiruzen achieved both. So yes, he achieved Victory.
You asked for the definition of victory and I showed it as well as Hiruzen achieved it.
Oro did not mean to "weaken" Konoha, he mean't to destroy it. Hiruzen meant to protect it and ensure its continued existance. Hence Oro failed and Hiruzen succeded.
Oro's arms weren't the only thing lost, but his ninjutsu as well. For a guy who is aiming to master all ninjutsu (hence why he was seeking out the sharingan and immortality) that was not a minor loss indeed.
Indeed with respect to Oro, Hiruzen's death only managed to satisfy his thirst for revenge. However, with respect to Hiruzen, his death sealed 3 kages from Edo, and reduced Oro as a threat to Konoha (he never attacked Konoha during his sealed state). And paved the way for Tsunade to inherit being the Hokage.
So yes, Hiruzen achived far more than Oro in that battle.
Back then it would be easy to think that was Orochimaru's main goal was the destruction of the leaf, but based on the fact that he simply used the sand for the attack and had a few sound ninja. If his goal was it's destruction he would have certainly placed more of an effort into it especially after sound fours leader falls ill. I also remember that he mentioned getting things in motion.
If anything his objective probably had a lot more to do with sasuke then anything else. Since Sasuke was an Uchiha and the fact that he known information on the tablet. In truth his goal could have very well involved the rinningan in the end rather then simply the sharingan.
Orochimaru did not exactly have a reason to attack, based on the fact that he had another step towards his goal sasuke uchiha. Especially if we take into account that he has an armies worth of curse mark users at his facilitates. Even without his arms he was still powerful so I don't see how sealing his arms did much other then slow him down from his goal of knowing everything. The sealing of said kages was no advantage since Orochimaru figured his way around that also.
So even with said definition the only thing the third did was delay orochimaru and prevent him from destroying the village something that was not high on the to do list. So where is the victory exactly. At best what happened was a minor annoyance for Orochimaru with only the pain of the effects being the biggest problem, and being pressed for time of transferring into a new body.