It is true that the lv 30 entry requirement hurt low level partying, but the reason it hurt partying is because most people don't enjoy the exp grind. If making a party were fun, easy and entertaining people would do it. As it is right now, there's no reason to not Gusgen to 30 and Abyssea to 99 if you're able.
I find Gusgen parties incredibly boring and generally only take my jobs to Abyssea when they can contribute at 70+.