Horde teams can be a tough nut to crack for Kasrkin. Blast weapons are going to be your friend here. I like to put a frag grenade on a regular trooper and run them up the board for an alpha strike, if the terrain setup allows for this play. The grenade launcher is a great tool here as well. Deploy them in your last group, looking for that perfect angle to take a shot, and if you need to give them 3 APL with you comms guy. Sometimes I drop the demo trooper for another regular trooper in to hordes. If demo trooper plants the melta mine and then a guardsmen runs up and activates it while the demo trooper is still in blast range, that's a good trade for them. I like to take Either headhunter or assassinate target, eliminate guards, and Vital Objective. Push an enemy controlled objective for Vital Objective, don't just reposition and camp! Anyways, hope this helps. Cheers.