Email tip from Fernandes90:
Easy ways to kill the armored kantus are to target them and have your team distract them, then sticky them with a frag and they die instantly. I had a problem where my whole team were using pistols except for one who I gave a flamethrower earlier and they were able to use that while everyone else who had boomshots and torque bows were forced to use the pistol. I got frustrated so the i decided to try to sticky them, it worked a lot better then your method, i took the armored kantus and theron guards and grenadiers out first Then I kept the Serapede for last and destroyed both of them. Hope this helps you and your followers.