seems to be incomplete so far, it wouldnt fit to have borg cubes as expendable as the normal ships ie 1 cube should generally be worth a whole fleet of ships, though more costly to build but can regenerate damage somehow.
The idea behind some of the borg encounters and assimilation is to gain a lot of bonuses to weapons and shields. It will have an automatic bonus to weapons and shields when it encounters its first player ship. Also the Assimilation Fleet is only a single cube. The ship spots are made for "asimilated" ships or ships destroyed in the first round of combat to add more combat bonuses. There can be technology that adds to more weapons and shield bonuses allows a cube to fire multiple times. However once you get a cube that is at 1+ weapons with 7 shields. A single borg cube becomes almost too much to handle no matter how many ships you have.
But yes this is a rough sketch and is very incomplete. In the early phase of the game the borg will be no powerful than any other empire but that is like TOS era where the Borg was not introduced. This should give the borg plenty of time to assimilate the delta quadrant systems and boost both weapons and shields before they make the transwarp conduit to the alpha/beta quadrant. By then the Borg will be a nightmare.