Okay, so let's say I do twenty Levi EX runs.
He autokills us in about twelve of them. Now, say that nobody in this group is using third party software. Our only conclusion is that "he seems to kill you if you do too much dps, maybe at about 20-25%?" - so what are DPS supposed to do, just literally do nothing in that whole phase after the spumes die? This is not reasonable (unless we use third party tools of course... where it's still poor design, but at least we can handle it).
Twisters are visual. Twintania has a cast bar. You can see it. You don't need any third party tools to deal with Twister. Also, this is not September, so I'm not sure how that is relevant.
You cannot accurately tell 20% on Levi's HP bar without a third party tool.
Also, you seem to be strawmanning us as saying "all mechanics which oneshot are bad design" when our argument is "raid-wiping mechanics which have no reasonable legally-visible pattern or predictable features are bad design".
