wesleybrouwer has provided some excellent information on this species which seems consistent with other information I've gathered on these animals. It seems that the care needs that match these toads most similar are along the lines of Phyllomedusa species, like a slightly more humid (mid-canopy) version of P. bicolor. Like P. bicolor they will survive in smaller tanks with less movement, more humidity, and less air movement, but show the best health and behavior when given a set up similar to some Panther Chameleon set ups I know! While a vertical tank gives an impression of more "room", these guys (like most arboreals) are still looking for footprint, they just want it above the floor of the tank, so I don't think putting them in a 40breeder vertical is actually giving them more usable space. A 60 breeder (same footprint but taller) would be a much better option, but still on the small side.
I do want to note that with at least a few of the breedings mentioned, they were with freshly imported animals and were not repeated in later years. I don't know much about Steve's experiences with them since I've not seen him give out details (at least not on the forums), but I know Reptile Depot's animals were fresh imports and not totally expected. I'd love to get more details on how tads were raised (Steve mentioned that they had the best success raising them in a pond set up) as it may play a part in the toadlet mortality. I also wonder about toadlet access to UV (more work needs to be done with this idea with amphibians - if the adults use a UV basking spot it may be important to the toadlets) as that can significantly influence toadlet growth and mortality in other toad species.
Other factors that influence died offs at that stage in life tend to be nutritional - either adult, tadpole, or early toadlet.
I think part of the issue with the toadlets not selling was the pure mass amount of them that were available for a relatively unknown animal. Two breedings produced a flood of them! I'm not sure they were overly flashy at that age either, and when you try and look up care for them it's basically unknown - the summary here from Wesley is the best I've seen so far.
Can anyone give descriptions on their WC care in more detail? I've worked with Rhacophorids from the same shipments, and suspect exporter care may play a part on why these animals are in tough shape (it's just too consist in the same issues with most of the frogs being exported!). I know treating for digestive parasites in particular is tricky, since the sudden death of a heavy load of parasites can lead to huge issues with bleeding and infections. Are there ideas on slowly lowering the populations of parasites (like fish keepers using garlic foods for imports) to get populations lower before the heavy duty treatments?