Title is the feedback, but here is a bit more. You have made a change that will prove detrimental to your companies income and have shown a gross misunderstanding of the F2P model and how it applies to the Dilithium Exchange.
Removing random loot from STFs in addition to the random prototype drops and having nothing in the game with a similar mechanic beyond the outdated Fleet Actions that nearly half of have been disabled due to how horrible they are. Especially in comparison to the STFs. Believe it or not, some players find the 'Joy of Discovery' when looting to be the most enjoyable part of the experience. What content do you want them to play now, and don't say fleet actions because that didn't get you the same playerbase that your STFs did nor do they have the prototype drops. And if you don't believe that the 'joy of discovery' is that important to some players look at your lockbox sales for a minute or two.
F2P Model & Dilithium Exchange
A F2P model is pretty much a form of subsidization. You have the players who pay more than they cost you in expenses, and those who do not. The goal then is to ensure that those who do not pay enough to cover the expense you incur because they play still provide an important role in the game. Typically that role is to improve the game experience of those who are paying more be it by lowering the wait time to form a group, or to farm the dilithium for them. Right now the Dil exchange is sitting at 160 dil : 1 zen and is fairly stable. With your current changes I would wager it will drop drastically, the only think that will keep it from falling into the gutter completely is when people stop spending their Zen because they do not feel they will get enough Dilithium for it. That is bad for obvious reasons. In reality cryptic the higher the value of zen to dil becomes the better off you are as that should increase the volume of zen being sold. And purchased.
Good luck guys, all I know is you better be pretty nimble and not take months to stabilize these issues for your sake. And in closing I would like to congratulate and remind you of your success, you are the #1 PWE game in North America. Do not loose sight of 'why'.