This mission can be very fast-paced out of the gate. You should first send the forces you started with in to the base where the catalyst launch facility is to control the situation. Meanwhile, build the following: A refinery (sell after harvester comes out) and ten rocket squads/three saboteurs. Build a SAM turret at your base to stave off future air attacks. After you have enough, send the rocket infantry and saboteurs toward the base. Go quickly, but try to keep them together. Get a saboteur into the construction yard and the entire base will be yours. Send one saboteur to capture the facility and another to get the reinforcement bay (four stealth tanks). At your base, during the process, make multiple rocket bikes (mobile AA) and flame tanks.
With your new #2 construction yard, build an emissary to make an expansion to the south. At your base, you will likely be getting attacked and must keep things under control. Push for the western base, without using the missile (If you choose to fail a secondary objective this is much easier). Use your flame tanks to burn everything to the ground while your rocket bikes provide AA support. Finish off the base and work on your expansions. You can take the western area now once you get some more solid AA and the area southeast of the new base is ripe as well. Two expansions will fund your army very well. Additionally, sending a few black hand accompanied by half a dozen or so rocket squads to the north of the base to stop the Scrin from leaping over the chasm. That will free you to capture the spike, further accelerating your income.
Keep up the anti-air production and build a few SAM turrets at the new bases (especially near the facility). But don't neglect the mobile anti-air units as they are essential when devastators come knocking!A group of stealth tanks at both bases would work great, but be rather expensive.
The actual assault itself is as straightforward as any other, when you get down to it. Just be sure to bring a variety of units and attack the #3 base first (northwestern corner) as the enemy may deploy a rift generator there.
If you find that you cannot defeat the enemy on the first rush, at least try to eliminate the rift generator! You should be able to recover from a loss and go back and finish the job with new knowledge of how the fight will go. Stealth tanks provide the ultimate anti-air against devastators. If one attacks, quickly focus their fire to bring it down. Make them top priority over the carriers as they can dish the most harm to units over an area, making everyone die faster. Repeat your steps to smash the final base and you're done.