People doing split farming will result in Blizzard Nerfing Horadric cache legendary chances, and that is it. Then those NOT abusing the system will get hurt, usual business.
The "somthing can be abused? Sure, let us get to it" mentality is SO far away from what I usually imagine myself doing in a video game that it is not even funny. People artificially lengthen their reward loops by jumping ahead of the pack, and then, they will complain ahead of everyone else that BLIZZ, NOTHING DROPS FOR ME, BUHUUU, I AM STUCK ON T4
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GG, I say. It will get nerfed, it has to. And it is not defensible. Just like goblin/tile/barrel /cellar farming was not fair (or even "fun") in early Inferno days.
And at the end of the day, stuff like this is why if you want competitive economy, you need to have a strict anti-abuse policy AND trading. D3 has none of these as of now. So whatever floats your boats, I guess.