On the contrary, Rio can tell you all that, unlike the armory. You can see how many runs they’ve completed in various timed brackets. The best run they’ve done for the dungeon they are applying to.
This is from the website but it shows up in the addon:-
There is no guarantee when you take on a random, they may be a great player but leave after one wipe, or they could leave the moment the key is put in, they could d/c, they could afk, they could be someone who has only ever done one of each +15 and bought them all.
The addon still gives you a better idea of the random you are taking on, as compared to blindly taking any applicant. Raider io is merely a reflection of their experience.
I would not expect anyone to take me to a +20 if I applied but I would expect to be invited to any +15 I applied to (providing they wanted a melee).