The point about Aegis and RUN is that SE wanted to make a magic tank when they had already buffed the crap out of PLD in regards to MDT. With the ability to get -87.5% MDT between Aegis, Shellra V, and a Defending Ring (You'd have a lot of other DT gear, of course, but that's not the point), there is absolutely no way RUN can compete with that. Epeolatry is a stop-gap, a bandaid, and for how expensive it is, it's not anywhere near good enough. RUN can't get MDT anywhere near as good as PLD can, because PLD can get that -87.5% to 8 elements at once, whereas RUN is limited to, at most, -72.5% to a single element. Not only is PLD capable of absorbing more magic damage, but RUN can't even get its own -MDT for a single element to the level PLD can for all of them.

SE kept buffing Aegis and kept buffing Aegis until they worked themselves into a corner. Any 'rebalancing' of Aegis is going to be a nerf, and, furthermore, it still won't fix the problem that already exists. Even if you bring Aegis' MDTII down to 25%, which is where it originally was, it's still better MDT for 8 elements than RUN can get for a single one. If you bring it down further, you have nerfed the thing to worse than its original, 75 version.

The only way they can put RUN where it was supposed to go, and make it was it was supposed to be, is majorly buffing its magic mitigation in some way. Majorly. And that is not possible without a serious change to how RUN functions, since RUN can only do three elements at a time, whereas PLD, again, can get more MDT against 8 elements than RUN can against 3. They just seriously, seriously have backed themselves into a corner. To make RUN a better magic tank than PLD would either require nerfing Aegis, or making RUN even sturdier against magic than PLD currently can be, which would make it practically invincible.