SPOILERS AHEAD for all games including JoH:
I would say that nothing is definitive until we get the full story, which to date we have not. At present it seems that there was an elven empire which erupted into civil war. This left some parts destroyed and other communities isolated from one another. One of these was the area known as Arlathan, which may have been the capital of the old empire but now just a regional centre, similar to but probably larger than the Temple of Mythal. They felt threatened by the encroaching humans and tried to keep them away. The humans retaliated and using blood magic, succeeded in defeating the elves.
Subsequent descendants of these elves told the story like the humans had destroyed the entire old civilisation. The Tevinter told the same tale because they also believed they had brought low the great elven empire - a matter of pride to them. Actually they only destroyed a bit. The tale among the elves got mixed up down the years so it was assumed that the humans were responsible for their loss of immortality, when in fact it was a combination of the fact that only certain noble elves probably ever had it and in any case had probably lost it at the time that the Dread Wolf shut away the gods. This is why the Dalish believe one thing, because they are descendants of the elves conquered by Tevinter, whereas Abelas and co believe something different because they have always been untouched. Luckily for them they were so far south the Tevinter Imperium never got as far as them. Bearing in mind how they have responded to intruders down the years, you can see why the ancient Tevinter might have got a bit narky with the elves of Arlathan if they did the same.
However, you cannot say the elves keep bringing about their own destruction. Even Orlesian historians are willing to concede that the conquering of the Dales was as much about Orlesian expansionism as a march of faith. JoH definitely suggests that there were tensions starting to arise between the two nations when Ameridan did his favour for Drakon. I'm not entirely convinced that Drakon failed to go I search of him because of the 2nd Blight since Ameridan recalls that Drakon wanted to keep things simple with regard to faith, unlike Ameridan who believed that the two religions could co-exist. So it was probably convenient that Ameridan wasn't around to voice his opinion on the matter when the Chantry started to press into the Dales. Had Ameridan returned he might also have encouraged his fellow elves to help fight the Blight instead of holding back. Then Drakon's son totally ignored the historical debt that his nation owed not only to Shartan but also to Ameridan. Without their actions Andraste would have been defeated much sooner and a horde of barbarians, led by a dragon god, would have fallen on the fledgling state of Orlais whilst its armies were otherwise engaged. Had the elves been total isolationists down the years, that is exactly what would have happened.
So whatever the elves might have been guilty of during history, mostly by omission, they didn't deserve what they got. Either slavery as a constant supply of magical blood for Tevinter rituals or poverty in alienages or recruited by the Qun or stateless wanderers. I'm rather hoping that at some point the elves are going to be allowed to have a revival in fortunes - at present I'm doing my best with my various elven Inquisitors.