Level 10 Dwarven fighter, +10 to hit, 1d10+1 (magic battle axe +1) damage, 4 attacks with disadvantage.
I also tested a Human Fighter with +11 to hit, 1d8+1 damage... negligable difference. I forgot to lower the damage for the offhand by 1 weapon size for both dual wielders... oops! And no finesse axe?
Use deadly strike with all dice on the first hit, and use glancing blow with all the dice on the first applicable miss (maybe its better to spread them out?)
This is a series of computer simulations of 3 million attacks each against 18 AC
Remember Critical hits do 8d6 extra damage with a magic weapon.
Expertise Dice only for deadly strike: 26.04 DPR
Expertise Dice also for glancing blow (max 3): 22.91 DPR
Expertise Dice also for glancing blow (max 1): 27.85 DPR
Expertise Dice also for composed attack (max 1 glancing): 25.23
Expertise Dice also for composed attack (no glancing): 25.12
Expertise Dice ONLY for composed attack (deadly strike crits): 21.34
*only 1 die is used for composed attack due to it being really bad (15 DPR)
It looks like you get +13 to +16 DPR if you cancel out disadvantage (you can't gain advantage).
Now compare to a human fighter with +11 to hit, 1d12 +5 + 1 damage, 2 attacks without disadvantage:
Expertise Dice only for deadly strike: 36.74 DPR
Expertise Dice also for glancing blow (max 3): 35.45 DPR
Expertise Dice also for glancing blow (max 1): 37.67 DPR
It looks like you get an additional 10 DPR if you have advantage
So you can see an interesting comparison of the different maneuvers here. The take home message is that you are losing 30% DPR by using two weapons so they should be used situationally. They aren't that bad once you reach level 10 but they it takes them a while to get that strong.
I did these calculations for level 1 fighters and dual wielding at that level is terrible, about half damage of normal fighting style. However, against a horde enemies who die in one hit* and have low* AC, it is advantageous to use two weapons.
* Enemies with both less than 5 HP and less than 12 AC for a level 1 fighter.
For level 10 fighters as above, 14 AC enemies shrink the gap to about 20%. 22 AC enemies grow this gap to about 45%
So... looking at the math... I personally find it a little bit questionable that you lose so much damage just for the ability to kill 2 targets in one turn (or score a finishing blow against a single enemy with low health). If you can manage to lose disadvantage regularly then it evens out though, so thats also something to consider. In addition, you get no additional penalties for attacking while prone, blinded, etc. Also, rolling 8 d20's is kind of excessive. but maybe thats your style.