Dynamis mobs can still kill you just as easily now as they could when the cap was 75.

People forget that they still all use their respective 2-hour abilities and mnk/war/rng mobs can still drop you pretty quickly.

Really doubt you'll get people having much success soloing, especially if it's still aggro stone > mobs pop. Jobs with a some sort of sleep might do OK but jobs like THF and DNC won't be soloing much, especially when they suddenly discover they can't evade shit without their cruor/atma buffs. So no I don't think they need to raise level.