I still can't think of anything that comes close to EverQuest. There are traps people can fall into, one dungeon is in a huge cavern made out of crystals and ice, and there are slippery floors so when you stop moving, your character keeps going... People can fall into some nasty situations in that place. One of the classes has the ability to summon others to them which would be a total life saver in those situations. Otherwise the person will likely die unless they are uber, but if they die another class can summon their corpse to you and then they can be resurrected. There are also some doors that need a Rogue to unlock. One brutal dungeon has a fake floor trap and if you fall through you land in a prison cell below with enemies in the room. If you even survive, other characters will likely need to help them escape.
The focus is mostly on the combat though and it is endlessly complex, or it seems it at first anyway. Some enemies are clumped together and if they see you, they will all attack together and it is sort of un-survivable. But several classes have some different ways to split up enemies like that. Some can do it after you have been attacked, but some can split the enemies before they even attack you. One of the ways is quite complex. But the bosses are the biggest thing about the game. For example one room has 4 spell caster enemies. 2 wizards that are stupidly powerful, and one is a class that can mind control a member of your party. Scary stuff. Each boss has unique mechanics that you have to figure out and overcome to win.
And yeah this is an MMO, but you can play it solo if you want to, you can even play it offline. I think the best way to play is offline by yourself, but with your own party. No game come close. Vanguard had more interactive dungeons with keys you had to find first, and events you needed to trigger before you could reach certain places etc.. One dungeon was a huge ant cave and there were crystals growing out of the walls which drain all your mana really fast if you stand near them. And you keep getting ambushed as you go through, so sometimes you have to run through a tunnel of enemies and crystals to get to an area up ahead away from the crystals. Scary... Deadly! Great game, but the combat in EverQuest was better overall.