What level are you at and how many allies do you have? I am at L 65 and I can assure you that even though I greatly over power an opponent I will loose units including many high value valor units.
I noticed a change in my loss ratio back when the game was opened up to the US. Many things suddenly changed, build times seemed to suddenly increase for example. Recently the game was modified yet again, the goals involving beating rivals have taken a big hit in terms of the amount of valor they give out, and there are a lot less challenges.
There are points at which adding allies no longer affect your attack and defense scores. At one time someone said that these numbers are not calculated in real time but I've noticed that depending on how many allies you have if you add or remove 1 your totals can go up or down. Oddly a couple of times I could have sworn that adding an ally caused my totals to go down. I've also seem my totals go down depending on what units I add, sometimes they go down even though I've added something and I believe it's mainly the low value units that make the differece as it looks like they might somehow displace or change an average value that the game is working with.
In any event being a strategy game that is modified at will by the devs without warning and this is apearantly common practce for Funziio makes for a very frustrating game since any long term strategies can be completely destroyed. Great example would be the fiasco with the stealth figates. At one point their cost was 175 valor but with the attack and defence scores that they have now. Suddenly their attack and defence values were cut in half. After many complained and some got refunds the cost suddenly was changed to 275 valor but their a and d values remained the same. Then a few days later suddenly the a and d values were bumped back up to where they were originally and what they are at now.