Kerrigan is a vile, evil, scheming ***** as we know from the video game. That is represented in her cards as well.
In stage I, Kerrigan is as likely to go for special victory as is Aldaris. She may choose all Z- and Y-axis, yes, but this is only really useful as there are only two or three players on the board. If there are more, the chance of a Navigation Error is over 50%, and then you stand in risk of loosing more than you gain with that card. Same goes for the two bases: you have much ressources, but are spread thin. That's ok if your neighbours like to build up for themselves, because you will be faster and attack them before they are ready, but when they attack you first you're pretty much screwed.
In the second stage, you may hasten the game which is useful with few players to quickly reach stage III, provided you have an edge before the others in reaching the special objective (which you should have since collecting CP comes naturally for knockdown when both reach the special victory), but normally you won't take it.. You go for Sarah herself, which is cool because the is the strongest heroe in the game. She splashes and kills good, but the low health values on Zerg cards are her achilles heel. Research everything that gives health if you want to keep her, especially the Ultralisk combat cards.
In stage III, you may give them heat. Either you have to get some things together to end the game in the next round, then you choose the Deathblow and attack golden up to four times to simply devestate the enemies forces and gain control of CP-areas. Or you already have them, then you can make one planet extremly difficult to conquer by preventing more than one order from every player on that planet.
Generally, a long game's not Kerrigans friend. Try to keep the speed high and give the weaklings what they deserve.