I played some of Doom Eternal today, and I made it to the ARC Complex. I knew that the Slayer Gates were meant to be challenging, but the latest one threw all sorts of enemies at me that I haven't seen yet in the story, like Barons of Hell (who look more intimidating this time around) and Cyberdemons (well, Tyrants, but come on,
they're totally Cyberdemons)
For whatever reason, the part of the game that I'm having the most trouble so far are the secret encounters, where I have to beat specific enemies (often really tough ones, or new ones) within a strict time limit. I had trouble with a secret encounter in the Super Gore Nest, and now I've found one where I have to beat a Pain Elemental, a Cacodemon, and a Arachnotron (and possible other lesser enemies) within 15-20 seconds (not sure of the exact time). At least grenades or sticky bombs work well against the Cacodemon, but I'll have to look up how to deal with the others.
While I haven't encountered any Marauders yet, I've seen footage of them in action, and I know that there's a secret encounter that requires you to beat one, so I'm not looking forward to that.
EDIT: beat my first Marauder. Barely, since I had the rune that saves me from death equipped, and I managed to kill it with rockets and a Glory Kill while everything was slowed down from that.