I saw a lot of posts answered with git gud, but it might not be very useful. So after surviving 50 days with the DLC in Legendary grandmaster, here is what worked for me.
Tips to Survive in Early Game
- Don’t accept no WP mission without a squad tailored to it (grenade specialists + specced Techmarine + servoskull apoth).
- Same for other risky assignments(3 marines, even no mastercrafter weapon can be a pain). It’s better to be safe than sorry.
- Only take the very best T1 items. Don’t waste Reqs on mediocre ones, and try to get melee + armor Req levels up ASAP.
Examples are: AoE melee weapons, + Mv armor, + Will armor. I also took the +50% XP blade.
My Squad composition is:
- Justicar*2 with honor the chapter.
- 1 purgator with psilencer.
- 1 Interceptor.
The Interceptor is not very impressive early, but has great potential.
The purgator psilencer can OS a lot of cultists at once, but he will usually required all his 3 actions to get into position, so honor the chapter will be critical.
Grenades are great to push people in the “void”. Abuse them this way. They also help getting some WP back for your justicars. Using Honor the chapter on each other also helps them replenish WP.
You don’t have to engage every group on the map to win, but make sure you pull opponents away from reinforcements when you are engaged against a group with another nearby.
Ignore storyline research requests, and get Quicksilver and Gates of Infinity ASAP (the first strategems, on the left).
Focus on getting warp drive early on (servitors -> warp drive -> reactor -> warp drive -> servitors -> whatever you want).