iLv needs to change

[synesthetic]

ILVL requirement only ensure that you are not too undergeared for this particular content, so making weapon requirements is pointless as even if it have greater weight in your performance it doesn't ensure in any way your success.

The biggest impact on performance is lack of skill, not a bad weapon.
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This is not even remotely true. Just checked myself. With i55 weapon I have 72% of dps of i135 weapon (40% drop).
You really underestimating the combined power of other gear slots. Vast amount of primary and secondary stats far outweigh additional weapon damage stat weapons have.

I never said anything about making weapon requirements, and never said groups fail because of people with small weapons.
Nor did I ever imply that all underperforming players are only in that state because of having small weapons; skill is a separate issue which I am not trying to address here.

I will take your point that my estimation on an i90 weapon vs. i135 was off.
Between figures I remember from progression as each endgame tier came out, and what I keep hearing in instances now, that estimation felt right.
A drop in damage by 28% is still a pretty big impact though..

I don't have a job with both an i135 and an i90, so I had to substitute using an i125 and i70 with approximately the same drop in damage.
Equipped with the i70, I did about 75% of what I could do with an i125 and my regular armor--similar result to your test. Cumulative iLv was 110.
Re-equipping the i125, and removing an earring to bring my cumulative iLv down to 110, I did 92.5%.
Also with the i125, and removing body armor to bring my cumulative iLv down to 110, I did 89%.
Each trial was a full skill cycle lasting 2:07. Can't really eliminate randomness like crits from the trials (well I sort of can, but I don't have time for that right now), but I think the results of each are still reasonable.

My main point still stands that item level does not properly reflect your character's potential, and is thus misleading.
Two people with the same item level, but one with a far smaller weapon, have extremely different potential. Even different armor slots are not equal.
Almost everyone here knows all of this already, probably because they either happened to read it or someone happened to tell them. There is no metric in the game that shows this. Item Level is the closest people have, and is referenced everywhere as being super important. The second-closest stat would be that... "Attack Power" and "Attack Magic Potency" stat that just mirrors your primary damage stat, making it also misleading and pretty useless.

The game pushes people to learn how to play their jobs, but does little to convey anything about how to effectively do so, beyond just pushing buttons. Stuff like this helps brew bad blood between "good" players and "bad" players. Changing how Item Level is calculated, or providing some means for players to at least make a better-informed decision on how to upgrade their gear, is just one thing I'd like to see happen to help lessen the gap, because I'm sure there are a lot of "bad" players who are honestly trying but just don't know better.