Cavern of Anger Bugged

Hi, great game. Cavern of Anger isn't resetting when I start a new instance for that area; I recently partied with a group and the odd thing was when we got there, there was already a party in there killing Merveil. So I say to myself okay we'll port back to town and create a new instance. When we do that and get back to Cavern of Anger, everything is still killed and Merveil is still dead. Please help so I can advance my toon, thanks

You probably need to create a new instance when you get to merveil.
Ctrl+click her entrance and make a new instance.

I just tried Ctrl + clicking on Merveil's Lair while not in a party and it just took me into the instance where my party had killed her without me there.

Merveil's Lair is actually part of the Cavern of Anger and not a separate instance. This is to prevent instance resetting abuse: there was a time in open beta where Merveil's Lair WAS a separate instance, and I recall abusing an easy cycle. Go in, kill Merveil, loot, exit the way I came in, reset instance, repeat. Now you need to redo the Cavern of Anger every time you want to fight Merveil.

Next time you're in Merveil's Lair, check your map overlay. If you move around a bit, you can see the rest of the Cavern of Anger on it. This is because the entrance to Merveil's Lair is just teleporting you to a different area of the same instance.