Their absence was the reason to ask that question. And indeed, that question WAS asked by fans, even having people come up with exactly that explosion to explain their idea. You're turning a blind eye to exactly everything that happened on forums such as this one, following the release of Z4.
The question of whether or not they perished over the course of the series and whether or not they died in the ending of Z3 are not the same thing. More on that later.
The only reason we ever shot down that idea was a lack of effects in Vile's Incident, and a few vague ideas in the back of the developers minds.
And Zero survived. Which happened in-game. His ride home was immobilized during the explosion.
The only way the Guardians' deaths make any sense is by rationalizing undepicted and unhinted off-screen events after the point. By that logic anything can happen without "changing the series." It's no different from having to re-interpret Z1's dialogue. Between Z3 and Z4, there is no reason to believe the Guardians to be dead. For them to be so is extraordinarily bad and unprofessional storytelling, even by MegaMan standards. Their only possible cause of death during Z3 yields 1 confirmed survivor (2 if you count Mother Elf), 3 unaccounted, 0 confirmed dead. You do the math. The sequel game makes no mention of their fate, the situation of their previous home leaves them outcasts, and forces usually associated with the player have been divided up due to the scale of current events. There is no reason in that scenario to question the Guardians' fate as of Z3's ending, not when no hint was ever given except for Zero's own survival, which works against it. As do other issues that Inti is content to glaze over.
Speculation as to the Guardians' deaths in the Zero-series,
for Z3, would have been senseless. But if in a pre-MMZOCW world you're wondering whether they sruvived the entire Zero series, it would have been far more credible if they had been struck by Ragnarok when Craft fired. Are you sure you're not confusing theories, Zan?
Either way, if they had died in one of Ragnarok's blasts, that I'd have bought under your "plothole rather than retcon" statement. But not Omega. Omega was done, overwith, and moved on, with what little information we had pointing towards survival. It was very little, yes. Z3 alone could not be taken as confirmation. But if the sequel moves on offering no further information, that indicates that no further information is needed, lending credit to the existing hints. If Zero survived, and the story-tellers see fit to offer no further comments, then the indication is that the Guardians survived. There has to be some counter-point as a reason to believe otherwise in order for the event to be considered questionable. That they do not appear in Z4 is insufficient, given both the scale of Operation Ragnarok and their general distaste for the idea of aiding Zero, it is very easily excusable.
Whatever rationale we apply, the basic facts that their absence does not deny presence, can not be denied.
If Phantom were not present, that would make sense. But the fact that the artist differentiated between them says that they're there in different states. You can say there's no rationale, but when you're rationale is coming from the exact same image you're questioning, it is very hard to ignore. The "time of death" speculation is the only means to rationalize it, and that comes about simply due to hindsight.
Speaking of which, arguing over the image in hindsight is completely pointless. Because Nakayama himself refused to commit to when that image is supposed to take place in the "revised" sequence of events, rationalizing the difference of effects is by no means necessary. Technically speaking, we don't even know that they're looking at Ragnarok. The matter of context, that being it appears in Vile's Incident, is the only thing gearing it towards that event. But once Aizu and co. have given the "fanservice; we just threw it in there" dismissal, even that can't be taken for granted. They could be looking at a comet on their way to fight Omega, for all we know.
We as fans should acknowledge exactly where that vagueness lies, and not cling so vehemently to our general distaste of the Guardians being killed in such a mundane manner.
Obviously. But how is that any different than acknowledging general vagueness in Z1?
Except, Zero did, by omission of the Guardians and later by MMZOCW's accord.
False. They said Operation Ragnarok, not Ragnarok the space station. Big difference.
The Resistance was split and Zero had assistance from other units, Joan supplying them with analysis, Colbor and crew evacuating Neo Arcadians, and who knows who sending Criore (or whatever the hell you name your super-elf). Zero may be taking out the big fish by himself, but in terms of Operation Ragnarok as a whole, no, he absolutely did not combat it alone.