Lasers and lightning are different things, so such an statement may straight up be too dubious for that, plus from
what I'm finding in the ASG Wiki, Star Dragon stuff is more likely to be a laser, and sadly it may not be calculable anyways out of either being off-screen or just not having anything to properly pixel-scale.
"Call down lightning" is still too vague to assume it's "natural" cloud to ground lightning, it doesn't help that it's one of his boss moves against Copen, in an
indoors place, so to assume that it's 8-C is sheer headcanon with the current stuff.
How I feel over a feat doesn't change how it's to be evaluated. 9-B feats often are remarked in a series as impressive in countless series, to say the least. There's verses where even 8-Cs can take over the world as I've said before, Hax and abilities exist to overpower regular weaponry, after all (See: countless verses ruled by 9-C zombies)
They would remain in the same tier, but not in the same level within it, remaining within a single tier and there still being AP gaps to stomp something below is pretty common. And as said before, such gaps are unquantificable, so at most you can only list a one-shooting level scaling chain if you want to detail how above they are.
Not necessarily, another feat within a closer range to 8-A (8-B, for example), or even Low 7-C could be used to support the cast being consistently within such a tier, context matters as well, after all.
Sorry, but an outlier is an outlier, this would be fine if it didn't lead into scaling the entire verse to a single feat that's far above the rest of the cast otherwise, as mentioned multiple times before.
Author intent is irrelevant outside WoG, we don't even take the OVA as canon, do we? We may as well say that GV got stomped by fodder if we go like that. I don't even remember any feat on it that goes beyond 9-A.
Absorbing all the energy over something doesn't necessarily means that you get to start making blows at the equivalent level of all of it at once without straight up immediately losing all of it on a single move. Either way I would like more context over the feat for this verse (As the calc seems to go for another verse) to be sure.