There are many reasons the bot is not performing well. All of them can be fixed, and here is how/why:
The main reason the robot is not doing much damage is a combination of the weapon choice and the fact that the reach is too short. Axes, as well as weapons such as saws and pole spikes, have normals, which restrict the weapon's ability to do damage by only allowing the weapon to do damage with certain faces. In this case, the axes have normals on the blade, meaning that the axe will only do damage when the blade comes in contact with another component. A better weapon choice would be Light Double-Sided teeth or Beater Bars, since those weapons do not have normals. Also, use a larger tribar for longer weapon reach.
As Badnik said (while I was typing this post, actually) there is too much weight invested in the drive power. With the exception of SnS (Sit 'n' Spin), spinner robots do not need to be fast, and thus, do not need very much drive power. Rather than use four NPCs with Pussycat wheels (it is generally a good idea to avoid Pussycat wheels), use the left and right NPC motors with Hypnodisc or Vlad wheels. An advantage of the left and right NPC motors is that, due to hitbox shenanigans, they can be placed so that most of the motor is actually outside the chassis while still being attached to the baseplate.
(https://gametechmods.com/uploads/images/61040Cutting Wedge IV 2.png)
Notice how the bodies of the NPC motors extend from the back of the robot.