I am not sure this is a Tier 3. Maybe 2.

My only real concern is that with two Battle Arts (martial artist and greater) you now have made monk almost completely useless.

The Battle Scion has a d12 hit die, great saves, better base attack bonus (which is enhanced further by other Battle arts), and can make up for the monk acrobatics, jumps and speed buffs with other battle arts.

There is very little this character cannot outdo a monk, or barbarian at. Just a matter of the right battle arts.

I think it can take on the pathfinder fighter as well, being dwarfed only by casters.

It will dominate the battlefield next to fighters and paladins until the average group level is high enough for the casters to take over.