Here is a list of things that have happened since man has created a tamerial empire. I am listing this because the next DLC or game will probably be about another Great War. This list will clarify the reasoning behind the Aldmeri Dominion and why they will go to war again.
1.) Snow Elves went extinct except for 1
2.) Wild Elves went extinct
3.) The first vampire was a human woman which brought the plague of vampirism
4.) The Tribunal Died
5.) Civil War in Skyrim
6.) Jagar Tharn kidnaps emperor
7.) Mehrunes Dagon almost kills everyone
8.) Vampires almost block out the sun
9.) Forsworn are created
10.) Dark Brotherhood is created
11.) Thieves Guild is created
12.) The Tribunal is killed
14.) A Akavir becomes a ruler over the empire
15.) Titus Mede turns his back on the Redguards.
16.) 2 Dozen wars
By now you are probably getting the point man seems to be more violent, and Nirn was much safer in Elven hands.
Now let's compare it to the elves' track record:
1) Dwemer enslave and turn Falmer into mutated goblin-like creatures.
2) Nerevar is murdered by his three most trusted friends.
3) Dwemer try to make themselves a god.
4) Night of Tears.
5) The Ayleids enslave the Nedes.
6) Dunmer raid Black Marsh and Elsweyr, dragging prisoners back to be slaves. This continues even after the Cyrodiilic Empire makes slave raiding other provinces illegal.
7) Morag Tong assassinate no fewer than four Reman Empire rulers, plus several heirs, throwing Tamriel into chaos. It supposedly goes on to become the Dark Brotherhood, depending on who you ask.
8) The Camoran Usurper storms his way though Tamriel leaving a bloody path in his wake.
9) Mankar Camoran ends the Septim lineage and creates the Oblivion Crisis. Those who died aiding him found themselves either killed by Daedra over and over, or dipped in magma, unable to stay dead.
10) Mannimarco plans some vague, sinister plans, with the help of some of the most sadistic people we've seen in a TES game.
11) Dagoth Ur tries to take over Morrowind and kill, drive mad, or mutate anyone who gets in his way.
12) Helseth kills King Llethan and his heir (probably), and anyone else who gets in his way. And compared to Morgiah and Almalexia, he still manages to be the lesser evil.
13) The Thalmor, between the Great War, their purges and their assassinations, kill scores of men and mer. Plus they want to destroy the world. One of them even tries to do so.