Its been stated that Elves, Dwarfs and Humans can breed with each other yet as far as I'm aware we haven't seen anyone who has had parents from separate races. I'd quite like to see that partly to simply see what they look like and partly to see how they are treated in society (probably very lowly). And if they are fertile as well then scientifically speaking Dwarfs, Elves and Humans are all the same species.
Also while were at it could we find out whether Qunari can breed with other races?
Not sure about qunari, but as others have posted, a half-human, half-elf will always be a human. It is not known if this is true over many generations, as in elf-born humans having children with elves over and over again, Gaider replied to me on that once and basically said genetics are not a thing in Thedas.
I thought a human/dwarf was also supposed to result in a human, but if Sandal is half-human, then that means half-dwarves are always dwarves. If he's half-elf, that means that elves are validly in danger of extinction.
No idea if qunari hybrids are possible, or fex for that matter, and if they are whether the child would be a hybrid or just one race or the other as with human/elf.