Ok Forest Haven is free, and is for lvl 1-13
Dark Forest is for lvl 1-18
Balefort Castle is for lvl 1-23
Fathom Crypt is for lvl 1- ? (what is its cap? )
The Lost Expedition is for lvl 1-30

Now, there are two problems here

1)why bother buying the other dungeons if you can buy The Lost Expedition straight away? Or have measures been put into place to ensure you dont get some stingy persons doing such a thing?

2) leechers. A little low level comes into the Lost Expedition, merrily staying afar and leaching exp and items. This is not very fair. Ignoring the fact that people will get annoyed, the leaching can be abused by people to power level a person quickly.

What I recommend is a minimum level cap to ensure that people are fighting the correct levels.
Forest Haven is lvl 1-13, no change there lol
Dark Forest is for lvl 7-18
Balefort Castle is for lvl 11-23
Fathom Crypt is for lvl 15- ?
The Lost Expedition is for lvl 19-30


Right now I feel an issue is that not all campaigns are played often. People tend to skip and be eager to get to the highest campaign (the lost expedition at the moment) as soon as possible. So I rarely see Fathom crypt maps, for example. By defining a level rage for maps, its more likely you'll be playing with people of your level and this way all the maps will get exposure.