With "no soil at all" you will not have much luck.

How wet is the constantly wet area? Sopping wet with water pooling in that area? More along the line of 'moist' but never getting dry?

Building up the soil with a 50/50 mix of peat moss and medium - large grade perlite might be helpful.

A buddy of mine had a AV I gave him that did surprisingly well in a very moist spot in his terr. There might be some ferns that might make it though you will have to research a bit as some actually prefer drier areas. You also might check into some cps ... there are Utricularias that like lots of moisture and might even have some Drosera that could handle it. While there are some pitcher plants that would possibly like the moisture levels, most get too big.

How good is your air circulation in the tank? That could very well be a big part of your problem if it isn't sufficient.

Also what is a "decent light set up"?

There is no pool (except at the bottom), just water constantly dripping down over everything.

The air circulation is pretty non-existant. The terrarium has a vent, but the top is covered so not much air comes in or leaves. I didn't even know circulation was much of a factor.

Sorry, but what's an "AV"?

I'll look into the peat/perlite mix, and do some research on some of the plants you mentioned. Thanks for the suggestions!

AV is African Violet.

For many plants, air circulation is a very big deal