There was a time however when the kol was a viable capital ship.
The time of the carrier caps. Esp the skirantra.
2,3 sometimes even 4 carrier cap starts. Bomber swarms were prevalent and difficult to counter. If you could get a kol to level 5 it was very usefull. However even then, the dunov was better. EMP + mappulse = dead sc and no AM or shields for the skirantras...not to mention sheild restore keeping each other alive. The only thing the kol could do was kill SC, nothing else. Whereas the dunov was very versatile, albeit requiring a good bit of micro.
But that time has passed.
I have easily played more than 1000 online competitive games of sins, going back to the beginning of the game. More than half probably 5v5s, almost all 3v3, 4v4 or 5v5. In all that time i have never seen capital ships massed produced in a competitive game. Even during the carrier cap era you would rarely see more than 5 capital ships per player, and a quick LRM rush would usually wipe clean a less than skilled player attempting a 3 carrier cap start.
Grimms guide speaks of late game bomber swarms, well i can tell you those used to be a problem. As were LRM masses. The corvette has changed everything, couple that with the LF buffs. And gone are both LRM masses and bomber swarms. Replaced with even larger masses of LF and/or corvette.
This makes the Marza one of the most powerfull late game units there is. Level 2 MB will wipe hundreds of LFs/corvettes in seconds. Couple that marza with an akkan and now its unkillable. The marza is also superb at clearing nuetral gravwells for colonizing, one of the best. Also is the best at bombing enemy planets.
The kol is completely useless cap, its good at killing large amounts of SC late game, problem is there isnt much of that anymore.
Early LF battles between equally skilled players will often come down to the capital ship. I have a marza you have a kol, i win. It is literally that simple.