Actually enemy resist reduces damage by 25% so if you attack an enemy that is resistant to your element, it reduces your damage by 25%. That means you deal 75% of your original damage or 1×0.75= 0.75 as nominal damage. Not 50%.
Greatly resist reduces your damage to 25% of the original damage or 1×0.25= 0.25 . Not 12.5%.
Effective basically removes that factor and especially on greatly resist enemies.
Although maybe codex definition of greatly resist could be wrong but effective does happen if you get past that 25% reduce resist to their own element (25% resist to fire for example means your fire attack deals 75% of the original damage).
Greatly resist reduces the element damage to that resist %. Enemy has 25% resist of the element so greatly resist definitely reduces all damage to just 25% of the original in that element. Immune probably means 0 or something but you can still damage immune enemies with your own element somehow .
Although the thing that reduces damage to 50% of the original could be when Midlumer says the enemy is saying shock resist on a shock enemy which is indeed correct if you take into account the innate 25% reduce resist. That probably means 0.25+0.25= 0.5 or 50% resistance to your damage .
So I think Midlumer is correct if it comes to that scenario.
Overall fantastic guide. It even taught me alot. I mean I already thought 90% weaken can increase your DMG to almost 2× aka ×1.9 and potentially reduce the resist from their innate 25% resist and potentially their add on greatly resist and/or resist on top of it.
It does seem that if you have 90% weaken, even in the worst of scenarios, your damage just gets to the original ×1 and in the best of scenarios , about ×2 or more.
I was thinking more on the lines of weaken reducing the innate enemy resists by 90% from 90% weaken so instead of 25% resist to element , its something like reducing damage by 12.5% instead and if higher weaken like 180% or 200% , 6.25% reduce damage from the element. Then the shock resist that is shown up on their also gets reduced to 6.25%.
It does seem that effective would be greatly reduced in effectiveness when weaken is used which is correct and even more so at higher reduce resist.
But if that were the case, greatly resist could be worse with weaken or maybe if weaken, greatly resist actually only reduce damage to 75% instead of 25%?
Although it's not far fetched to say that weaken also adds to your nominal damage so that you deal ×2 damage or ×3 possibly because even on greatly resist enemies, they seem to be relatively easy. Midlumer is definitely on the lines of correct or very close but there are some things that are hard to be so sure about. It really takes testing
From testing though, it's definitely hard to say but it feels from the damage numbers I've seen that Midlumer is correct. I deal up to 40B damage deadly strike from brutal and if weaken, I have seen double that sometimes hard to be too sure but it should be mostly correct.