The vivarium you build is going to be more of what you want for a viv. The drainage area is a place to allow for water to filter down through the substrate and collect below that substrate. If not there, the substrate would eventually become saturated and rot requiring replacement over time. Also, many plant's root systems would have issue with no drainage unless they were plants that thrive on wet soil conditions such as aquatic plants.

There is no need for a pond with dart frogs, but some individuals love the idea of the water feature. Some darts will actually stand in the pond area but its recommended to not have the water level deeper than what the frog can stand in.
The water, especially water with movement such as a drip system or waterfall, will help with humidity, but a sealed up tank with plenty of live plants, a misting system or fogger, will keep your humidity high enough.
I've seen pond areas with no filter system, but you would need to siphon out the water routinely and replace the water.
Since the overflow is already there, looking at Mikes build, you wouldn't have to create an area to access the pump and run hoses since your overflow is already there to hide a pump and hoses.


I think the main thing to determine when designing your build is whether you want a water feature or not.