if the frogs require the same things it is possible, i choose to keep seperate becuse you can then give each species its own requirments without hamppering the others needs.
this info is based on theese being the 2 frogs you mean... if i have got wrong im sorry, normally go by scientific/latin names...
the main problem is the tiger legs only get 1.5 - 2 inch and the goldens 2 - 4 inch, which is enough to suggest it wont work as the tiger legs would be out muscled in the hunt for food. the other problem is goldens are bulky jumpy frogs and tiger legs are slender moving frogs. also the golden comes from asia and the tiger leg is south american. the temps are around the same 27 being good for both though.
if you want to keep tree frogs height is much more important than length. for a pair of tiger legs you would need a 20 gallon minimum tank as they are very active, so for 2 species with a pair of each your talking at least a 40 gallon being the smallest possible IMO, so as they have enough room and can avoid each other...
exo terra do a 18" x 18" x 24" (WxDxH) which is around 36 gallons
as for the darts they are best kept alone, have very different needs. darts are not poisonus in captivity, but please dont add them.
if you want different looking frogs together the best to go for are read frogs as there are many different morphs and would be fine together.