You are making my point, really. And I do think you're being obtuse.

"If a mage is perma invis like you say, then they are not going to be in a situation where you can catch them even if you can see invis."

Why? What does that even mean.

Everything boils down to this: few or no mages at all, and when there is a mage, virtually always invisible. This gives battle applicant - the player - zero fun. And it can last forever.

The change means the battle applicant - the player - can choose to level up to 25 and get detect invisible. It won't change the scarcity of mages, but it will give just a bit better chance for the applicant - player - to be able to do what the requirement demands, hunt a mage. The mage still has all the advantages, but it's just a tiny bit less impossible. It's still up to the applicant player to get that kill, and it still may take forever, but at least it's not the near impossibility it is now with a total block ability, which invisibility is.

You keep making assumptions and not relying on the basic facts, which are facts. And I'm not doing this because of only my experience, though no, my last characters were not killed by mages. And no, mages at level 25 don't often come. But again, this is all irrelevant.

The change harms no one, it does not reduce mage play because as you seem to think, by level 25 they would come at you anyway, so they want to fight, and no applicant under 25, kill or no kill, gets detect invis.

Make the change.