Why not buff armor on Tabi instead of it's passive?

I mean, Tabi's passive sounds like really hard thing to balance, as on top there are champions who do most damage by their basic attacks, and ones who do only a little.

Dominating toplaners are either magic-damage oriented or caster-ish AD's, except for Yasuo, so this buff doesn't seem very helpful for bruisers struggling in the meta, it seems like random buff because "nobody bothers to buy Tabi anymore".

Only thing that buffing this passive becomes relevant is against lategame crit-build marksman, and even than it's best on tanks. So if not buff armor maybe give it passive similar to Omen's? Because current iteration of Tabi buffs will only screw up bruiser even harder, instead of helping them.