After giving the matter some though, my assessment is fairly simple. In terms of damage output and tanking ability, the SB's feel about right, except the Transcencia which is... buggy and curiously underpowered considering it's listed damage output. I suspect it's weapons, particularly it's default Plasma Cannons, miss a hell of a lot.
Range, for all starbases, seems to be a rather major issue - people have, thus far, proposed some rather ludicrous buffs to starbase attack ranges, oftentimes suggesting that they should cover a significant majority of a given gravity well.
I, however have a different idea, consisting of pretty much two parts. The first would indeed be a range increase, though not as extreme as most are proposing -- something along the lines of a 60 - 80% range increase for short and mid ranged weapons systems, and a ~50% increase to long range weaponry.
The second would be the ability for starbases and all other facilities (excluding, naturally, the Vasari Orkulus) to move in an orbital path around the world to which they're attached. This would render circumventing defenses a far more difficult task.
Finally, Starbases are either vulnerable to the point of uselessness or completely bypassable while defending an unihabitable node. Given the early information available, this does not seem to have been intended. My suggestion for this problem is quite simple; over an inhabitable node, Starbases have options available to help increase the resilience and prevent colonization of said node (or are at least supposed to - they currently seem to be bugged.) For a Starbase in an uninhabitable node, I suggest that this ability, which in such a place is useless anyway, be replaced by researched option that would allow the base to acquire a constructor and a number of tactical slots, which would allow for the creation of adequate defenses, locking the route down with phase inhibitors, etc.