In the main story, at the Temple of Mythal and shortly after, you will learn from a being called Abelas that it was not Tevinter who destroyed Elvhenan and Arlathan. Additionally, Solas later tells you that Vallaslin is the mark of a slave during the days of Elvhenan, something akin to thee Casteless' Brand in Orzammar I suppose. Which then implies that Elvhenan was probably destroyed by their slave rebellion, the slaves being the Dalish Elves of today, with the help of ancient Tevinter.
My guess is they wanted to make Elves in DAI look scrawny and underfed for this very reason. The information we get from game suggests that the Dalish Elves were former slaves of ancient Elvhenan. Now their are nomads. For nomads who were former slaves cannot come by much food and that naturally means they would be somewhat impoverished and underfed. I mean if you look at nomadic cultures in reality you would see that there are not many tough mofos or even well fed people among them.
Also, in the post credits scene, Solas is revealed to be Fen'Harel which means Solas is not a typical male elf.