I experienced one of those changes myself, when i played for 2 years on epic , had the luck to dominate a dragon(that after another secret change to the difficulty to dominate them) and i fed it every day for 1 and half year and managed to get 2 dragons on serenity and an egg which was ready to pop . I then decide to join JK on elevation and kill the dragons so we get drake for everyone in our village. To our surprise the drop rates were changed behind closed doors and all the work i've done was now worth 5-10% of what it should have been, that after killing the first dragon.
I then ask the GM's what to do about it and they tell me not to do anything. then the next day the change is official in the patch notes and they say they will refund me some of the drake hide the said dragon should drop on avg, but when i ask about the other 2 dragons he say he can't refund for those as i didn't kill them before the patch note was official. so yeah i was mad for a while, sold the account i was playing on at the time (Gomeo) , quit for a while and tried to forget that it ever happened.
I got back into the game a while ago, bought another account fully knowing that there will be another one of those changes in the future.
I really hope they will get they'r stuff together and try not to hurt players with more unexpected changes .
i think they should have a rule , where any game changing update /decision they make should be delayed for 1 month from announcing it till they execute it. and also provide enough details so we can understand exactly what will change into what.