Galio is supposed to be a tanky mage that goes into battle and smashes everything.
Right now he is more a squishy burst mage that pokes from afar and, well, still destroys (doesn't smash) everything.
Galio's role is to SMASH stuff, and this aspect is the most present in his kit with his ult and passive. Rather than giving him ranged damages, I would prefer him to rush into battle as his fists shatters the earth and the bodies of his ennemies.
My suggestions are:
●Reduce the AP ratios on his Q and W
●Reduce the max health damages per AP of his Q
●Increase the AP ratios on his passive and E
●Increase the cooldown reduction of his passive via spells so he can SMASH stuff even more.
●Increase his size a bit so he looks more intimidating
TL;DR: Shift his power from his Q into his melee abilities, especially his passive.