Suggestion:Improve the hero quest.
Pros: You can actually complete them.
In image below you will see what I'm fighting.
level 18 primary : 19165 rebel snipers vs 1000 archers. I think I got this.
You can complete them, you just need to understand the fighting mechanics.
For your example, you were Assault and given 1000 Rhine Archers with a base attack of 85. So without any hero bonus at all, that is 85,000 capacity for fighting.
The one you highlighted was 19,165 Rebel Snipers. Now because you were assaulting with archers their base defense is 5. So their total capacity is 95825 against you.
With 85,000 vs 95,825 you would only need a hero bonus of +11 to alter it to be 96,000 vs 95,825. Something very easy to do with a hero, thus your hero quest is more than within your grasp.