Disclaimer: Note that the only classes I haven't played are Ninja, Warrior, Monk and Archer so what I view from those classes are purely from a bystander perspective.
The existing skill changes compilation I read were from here. It seems like there's a lot of nerf in AoE damage, defensive buffs and debuffs. There are also buffs in attack skills in general.
Particular skill changes that caught my attention:
Enhanced Medica replacing Proshell - This is incredibly awesome given that Cure III range is so crap. This means that we can be more liberal on our AoE heals. Proshell removal is probably just to balance between all 3 healers so when Scholars get paired with Astrologians, they don't feel like they missed out on anything.
Quick Stoneskin replacing Graniteskin - Awesome also. Graniteskin removal, like Proshell removal, is probably for balancing out the 3 healers. Quick Stoneskin is actually very nice for tank busting mechanics and PVP where cast time really matters.
Selene Changes - Wow, looks like a lot of changes for the Scholar pet. The 'mass leeches' skill can be useful I guess, but with statuses that cannot be removed, it's hard to conclude it's usefulness. It will probably be good in a couple of fights here and there though.
New Class Skills
The Chakra mechanic looks like a throwback to Monks in RO1, so we might see Monks become more bursty depending on what they can do with it.
Aaaand that's it!^^