Yeah honestly I would recommend staying away from portcrystals to most people on their first time through. It would be even easier to recommend that if there was just a bit more variety in enemy types and placements, especially between Cassardis and Gran Soren, but I dunno just traveling everywhere via menu is boring and makes the world smaller.
And holy crap griffin taming sounds awesome! You could limit it in a couple ways, like requiring a consumable item to do it, and maybe adding in some risk reward, like having there be a small chance that an even bigger monster will drop down on you while you're flying around, knock you to the ground, and then you have to fight it. Maybe your buddy griffin will help. You could also use that to expand the world, maybe have some places only accessible by griffon or something.