(You'll find that instead of quest progression, I'm using the tactical score which measures how interesting the instance is.)
Recently, I managed to get my hands on the 2 instances that are to be purchased separately and got to run them a few times. First up is the Inn of the Forsaken, a 3-man for lvls 20-75.
Inn of the Forsaken (20-75)
This lvl 20-75 scaling instance takes place in, but mostly under, the Forsaken Inn. The inn is the perfect lodging for anyone travelling east, but lately those sleeping there have been plagued with strange noises coming from the basement. It features an (imo) interesting story which can be pieced together by finding journal pieces.
This instance is quite different from the others, featuring more puzzle-like gameplay than normal combats.
There's a lot of different objects you'll find here, some of which can only be used by certain classes.
The single non-boss mob is spawned by destroyable bone-piles, so be sure to go after those first.
There are 2 types of traps in this instance as well. Spike-traps that trigger when you (or any other creature) walk over them and the spinning blade-traps use tile-triggers on the ground.
It's time to use your emotes when you want to get past the riddle-doors, which can have one of over to 80 different riddles!
There are also (as mentioned earlier) some objects that can only be used by some classes (they're divided in different groups: lore, aware and brawn). There're trap mechanisms (temporarily stop traps), incantation stones (a magical effect happens) and runetablets (which give info) and suspicious walls (can be broken).
One other fun thing to mention is the water slide which leads to an awesome arena for the end fights.
The tier 1 boss requires a bit of strategy as you'll need to use the traps to your advantage as they can break his shield and stop his skills.
If you're running tier 2, you'll get to fight an additional boss, who turns the tables and uses the traps against you!
Price/Value: 1/5 (395 is quite a lot for a single instance. I'd wait on getting this until you have at the least a way of getting to cap.)
Storyline: 4/5 (Quite a nice storyline. A good amount of details and interesting bosses. Only downside is that it doesn't really tie in to the lore or any other story.)
Atmosphere: 3.5/5 (Going down you'll notice the gradual change from masonry and tomb-like structure to natural caverns. The riddle-doors look awesome as does the end-area. Downside is that you've seen tombs a lot already.)
Tactical: 5/5 (Though you don't need it, there's a lot of stuff that'll make you want a varied group. The traps are unique and the bosses are interesting.)
Overall score: 13.5/20
Get this after you got everything else you want and at the least try and get a way to lvl cap first.
The biggest downside to these instances is they're rarely being run.