I'll agree that there are some problems with how they marketed the game.
Ultimately, any player should be smart enough to view this as a game and not an investment. With that said, I acknowledge that they have marketed it all along as a way of making money. They post stuff about ROI all the time, and they even have the tagline "Get Paid to Rule your World". When they market it like that they have to accept that people will be upset when they change rules in a way that impacts ROI.
Personally, I think the best way to fix this issue given the rule changes would be the offer a refund (for a limited time) on those troops you bought. You took a risk you shouldn't have (it is a beta you chose to play), but I think they would make a lot of players happier.