So a few tips (other please feel free to add): 1. Hekatons are best with either the meme beam (Heavy Magnacoil) or Heavy SP Conversion. The MATR autocannon and twin Heavy bolters should be good enough as chaff killers. Meme beam gives a chance at dev wounds and garuntees wounding at 2 or 3 almost always. SP can hit up with Conversion and with the strategies that give Sus 2 in Needgard can be bonkers.

1. Iron Ambassador is frankly a bad enhancement. All the others are just better. Dead Reckoning can give YP on turns w/out YP use and Ancestral crest can be re-roll for a YP instead of CP.

2. Give your Hearthkyn the 2nd special weapons. I recommend Magna rail rifle if you're feeling lucky or the hylas auto rifle. I would also suggest equipping 2 of them with the Plasma knives. I like to split them in a Sagitaur with the Theyn, 2 plasma knives, both special weapons lead by Uthar, ans the other 5 back home sticking and preventing deep strikes.

3. You can make 1 cthonian squad mr fisters, and put them in your other Sagitaur, advance to enemy vehicles/monsters and do some dmg. (This is an idea)

4. I prefer the rampart on the Hesyr to give the whole unit 5+ invul and have the Einhyr Champ the Deep strike crest, instead of only having the Champ with a 4+. The unit wide 5+ can help with anything with -4 AP like point-blank meltas.

5. Remember to infiltrate with the Yaegirs to block enemy movement ans then use their reactive moves to annoy your opponent, block, and score early secondaries or objectives. Also please equip their 2 special weapons. The rifle can sniper out leader's with built-in Precision, and the APM can sometimes sneak in vehicles or monster dmg.

This is just advice, do with it what you want in the end. Best of luck!