NIN losing hate from lost shadows is no different than a PLD or WAR getting the hate beaten off of him really. And after Ni is acquired, a good NIN may never get hit, and thusly the hate is never beaten off the tank. The only way the NIN would lose hate in that situation is if another job simply accrued more enmity than the NIN has already built.
Although I like that kind of setup as much as anyone, SE are probably doing this because in the hands of a skilled player, NIN, while efficient, was broken. That's the only explanation I can give for this change to the job. This will just mean NINs won't be able to half *** their way through the job anymore. It was already mentioned, but now NIN tanks will have no choice but to spam Ninjustsu and chuck shurikens like there's no tomorrow if they intend to keep that hate without a good THF. Maybe even with one. The major downside is now the casual player won't be able to do this job as effectively lots of +enmity gear.
If they're doing this change to promote more DD Ninja, I don't know how well that'd be accepted by the populace of Vana'diel if they don't increase the NIN's damage potential. Not enough NINs use Shurikens to show how powerful they can be, and more people would probably prefer a RDM over a NIN enfeebler, since RDMs are primarily picked for their Refreshing abilities, the fact that RDM can enfeeble is just a happy coincidence. Not to mention Dispel. If there are no RDMs, I don't think most parties will say "OK we'll get a NIN and set out." I don't think I've ever heard a party say "OK we need an enfeebler," only "OK we need a RDM" and that's simply due to Refresh and Dispel. So I don't know what to make of this idea.
I don't know what's up with the RNG thing. They mentioned it depends on the bow? Well, thinking of FFT, maybe you have to be far away for Longbows, close range for Crossbows, and Shortbows are probably the same as Crossbows. I don't know about Guns but they had a huge range in FFT. They'll probably be the same distance as Longbows.
I don't play either of these jobs so I'm obviously not feeling the same impact as other people. But I'd say don't go getting too upset yet, not until we see just how they'll be implemented. SE is the master of vagueness.