Elimination involves taking out multiple dreadnoughts before extracting. There are no swarms on elimination, but an occasional group of enemies will harass the players once and a while. There are also many ambient mobs, and the large caves often have plenty of space for leeches and spitballers.
Similar to egghunt, you will land in a starting room with 3 tunnels leading to various caves, some of which will contain a dreadnought cocoon. It can be a good idea to use this cave as a hub, and I would recommend waypointing it.
When eliminating dreadnoughts, make sure you are prepared and have everyone ready. You might want to clear the surrounding area before you begin the fight. Engineers can set up turrets, drillers can place down detpacks (press R to place down multiple) and scouts can light up the area.
When ready, pop the cocoon and the dreadnought will begin to focus a player. That player should distract the dreadnought and try to expose the back to the rest of the team. Eventually the dreadnought will switch targets. Watch out for the dreadnought’s fireball and ground slam which both have their own telegraph.
When you destroy his outer shell, he will then begin to summon reinforcements when he roars and will become faster over time. Ideally you will want to kill him before reinforcements arrive. Do not waste ammo on said reinforcements, as the dreadnought will keep spawning them, focus the dreadnought instead.
Often using the hub cave will allow easy access to the droppod.