Just how responsible for the Flood of Light was Hydaelyn?

[Cilia]

Do keep in mind that it has been implied on a number of occasions that the Source could meet the same fate as the First if the Warrior of Light continues like they have. The fact that Hydaelyn entreats (or compels, depending on whether or not you accept the possibility of tempering) the WoL to keep at it is intriguing, though we do not know for certain if Hydaelyn is even aware of the fact that the scales are starting to tip too far.

Also keep in mind that the source of this information is Elidibus, who has a vested interest in having Dark triumph over Light. His comments on the matter are less about "Stop or there'll be a Flood!", more about "Stop or we can't win!" As shown by Emet-Selch's disdain for the Light-infested territories of Norvrandt, Light is also anathema to them.

I'm still waiting for Lahabrea's ominous warning from 2.0 to be clarified... given as most everything else has been.

[Absimiliard]

Also keep in mind that the source of this information is Elidibus, who has a vested interest in having Dark triumph over Light. His comments on the matter are less about "Stop or there'll be a Flood!", more about "Stop or we can't win!" As shown by Emet-Selch's disdain for the Light-infested territories of Norvrandt, Light is also anathema to them.

I'm still waiting for Lahabrea's ominous warning from 2.0 to be clarified... given as most everything else has been.

Urianger has also expressed concerns for the state of the balance. While I would tend to take what Elidibus and Lahabrea say with a grain of salt until proven or disproven, we know that Urianger is an exceedingly well learned individual that has the Source's best interests at heart.

As for Lahabrea... I'm beginning to wonder if SE didn't just sweep him under the rug at this point. It's pretty likely that a lot of his hammy writing was the result of them not yet having Ascian lore all that well fleshed out. Ascian appearances throughout 1.0 and ARR typically made them come off as mustache twirling villains of lolderkness. Maybe they'll use the frequent host hopping to explain why Lahabrea seemed to be completely off his rocker? It would be a pretty valid excuse. Emet-Selch already told us of the consequences of hopping bodies too often. What's to say doing it habitually wouldn't lead to psychological damage to go with the severely diminished powers? Anywho, I went off on a tangent, my bad. Tl:dr: Lahabrea was such a nutball courtesy of incomplete Ascian lore that we may never find out what he meant.

this isn't necessarily the case, but what we thought was the case due to our understanding at the time.

And what of Urianger's far more recent comments on the subject?

[Iscah]

Urianger has also expressed concerns for the state of the balance. While I would tend to take what Elidibus and Lahabrea say with a grain of salt until proven or disproven, we know that Urianger is an exceedingly well learned individual that has the Source's best interests at heart.

Which comments are you thinking of specifically?

[YianKutku]

Urianger has also expressed concerns for the state of the balance. While I would tend to take what Elidibus and Lahabrea say with a grain of salt until proven or disproven, we know that Urianger is an exceedingly well learned individual that has the Source's best interests at heart.

You may have conflated Elidibus's words with Urianger's words. Elidibus tells us that if we continue on as we do on the Source, ie righting wrongs and saving people, the Source will have an imbalance towards Light. Urianger later says that there seems to be an odd imbalance of the Source's aether towards Light (or at least Umbral), which worries him.

So the assumption a lot of players made, which is probably similar to that of the in-universe characters, is that the Warrior of Light's actions were directly responsible for this potential imbalance towards Light.

Except this is playing right into Elidibus's trap of saying cryptic things that are technically true, but not actually the whole truth. Elidibus is technically correct in that if we continue righting wrongs and saving people, the Source will have an imbalance towards Light, because the Ascians will make it so. And our "path" will bring us into conflict with the Garlean Empire (who does plenty of wrongs and produces many people to be saved), and it is the Garlean Empire who will unleash Black Rose to stave off their own defeat, because the Ascians manipulated them to do so. This is proven to be true in the Exarch's Bad Future, courtesy of our Echo-vision, so we can take it as more or less objective fact.

Meanwhile, Urianger's concerns over the imbalance on the Source is just that: his own (rightful) concerns, but also simply taking into account the current consequences of the link between the First and the Source resulting in an over-abundance of Umbral polarity, devoid of any causation. (We now know he was keeping his secrets about what the Exarch told him, but that's not really relevant.)

In other words, it is technically true that if we "continued on our path" the Source would have fallen to an imbalance of Light, but that leaves out the more pertinent truth that it is all due to Ascian meddling. Without Ascian involvement, our own actions would have been perfectly fine. With Ascian involvement, our actions would have made only a minor effect at most, since the Ascians (via Emet-Selch) told us that they would have done the Light-rejoining anyway, sooner or later.

In other words, we (or Hydaelyn) are not responsible for the Flood of Light in any way. It's all Ascians.