KinkiestSins, about your whole "World Soul" thing. World Souls are NOT Sentient Planets.
World Souls START off as living Energy. The energy then forms a Planet around itself so that it could be protected when maturing. Then, that Planet would have generations of Life both thriving and dying on it. However, when the time comes, the "World Soul" would mature, becoming a Titan. Beings made up of Clouds, Water, magic, life, and so forth. Oh, and they're also the size of Planets.
That DOESN'T make then 5-B, however. If a Titan was corrupted by the Old Gods, then not even the Pantheon themselves could stop it. It would basically make the Universe its own play ground, as well a portal for the Void Lords to enter in (Since, well, they cannot physically enter themselves. And, even when they could, it was only for a limited time).
Sargeras' battle with the Pantheon alone destroyed part of Reality. It destroyed Planet, Star Systems, and much more. That is, until Sargeras won.
http://ptr.wowhead.com/spell=256544/end-of-all-things
This is Argus' Ability for phase 4. Sure, it may be like Algalon's Big Bang, or something like that. But, to be honest, it might not actually be that case.
Remember, Yogg'Saron's World Destruction thing, and Algalon's big bang are just regular boss mechanics. Here, this is apart of phase 4. And, while a mechanic, it's a HEAVY piece in the lore, since you're also trying to get back to life during the beginning of that very same phase. So, it's bascially a race around the clock, pretty much.
So, if that's the case, then we could assume that Argus' End of all thing's ability ISN'T an overstatement, and that he actually CAN Destroy the Universe (Which IS stated in Aggramar's Description, talking about him guarding a Power that could unmake the Universe. AKA, Argus).
That's NO 5-B Feat. None of the Titan's are 5-B. They're ranging from 3-B to High 3-A Max (Or, 2-A if the "Universe" Is actually the Multiverse, in Argus' case).