The rudeness is uncalled for.
8.3 is tuned towards corruption. An ilvl will not give you any indication if that player has any corruption or even the right corruptions for their class, it will also not show if they have the right essences.
You can see someone’s score, which is an overall reflection of their mythic plus experience. You can see the highest key they’ve done in the key they are applying to. Also relevant experience. You can see the highest key they have done overall, also relevant experience. You can see how many keys they have done in each bracket. How many +5s they’ve timed, how many +15s they’ve timed, how many +20s they’ve timed etc.
If an alt has at least 200/250 score it will also show the person’s main score. So you know the group will know you have some idea of the tactics they are about to face. It does not guarantee they know the role but it will tell you if their score is for tank/heal/dps.
If it’s a +8 or something no one is likely to care that much. If it’s a +15 or higher it will depend on what the group’s aim is. Either to just do a weekly or they will want to time it and push further.
Raider io is purely factual data. It does not discriminate, it includes all runs by all as long as you got to the end of the dungeon and finished it. It is like the armory only better, because it includes all runs.