The boss seems to autocharge for no reason, making it impossible to even move around on the map properly, also its extremely weak on small maps (like Warebloom) , even 32k HP are not enough for 19 Players, one Heavy-Medic Team can take away over half of the HP, which is redicolous since the hitbox is so large even the worst player on earth can hit it with ease.
The Rage is also pretty useless in this case, so you might think about making him kill trough uber like Mummy or give him a buff elsewhere so its not dead right from the beginning because no one wants to play it (see Heavy Sauce).
As you are very quick in deleting any advantage for the engineer class, you might finally see that the medic also needs lots of nerf because its OP against ANY large and slow boss, at least on small maps.

Cheers

Hence, it's a WIP. But feedback could help I guess.