I want to express the immense disappointment this decision is. Obviously one of the least popular decisions that's been made in awhile, but it's legitimately worse than I think y'all realize.
The main gameplay loop in this game, is to unlock a character, upgrade their abilities, and gear them up to relics, and then do it again with another... And one of the MAIN components of that, is Injector pieces, and zetas. Removing 15% of the assault battle income for these is a small change for now, but in the future this could be catastrophic for new-midgame player progression.
At the extreme, assuming we get 2 new assault battles per year (based on the current rate with DotF and Peridia Patrol), we'll be down to 50% of the prior income, or worst case scenario, if the new ones aren't getting rotated too, possibly 0%.
In my opinion, there needs to be a SERIOUSLY good change made for the playerbase, since this last 2 months has been almost entirely disappointment and bad news.
(Punishing One/Tie Dagger making fleets awful to play, and rotating assault battles... Not much happens in this game tbh) - So 2 wildy unpopular changes, to one semi-nice to have change (GL tickets) is really making multiple people in my guild consider quitting.
-- Personal Testimony now --
If Assault battles turn into something like the raids (We have to push for them, or else we lose rewards every month) then that's a strong indication that there's nothing left for me in the game. I signed up for permanent progress and improvement. My line in the sand is here, I won't be buying any more crystals unless we see some sort of positive change.
(The raids being cycling content is fine, it's a good trade for better rewards than before they rotated)
When DotF was released, I thought it was one of the BEST ideas ever... Incentivize people to work on the new release, and add some rewards into the economy for doing it. Peridia Patrol was also another step in the right direction. But the negative prodding toward the new stuff (by dumpstering the old) is something I have enough respect for myself as a player, to avoid.
Honestly, I was literally one message away from uninstalling the game after this announcement, since it represents a shift into scary territory as a game. The only thing stopping that is the guild I'm in, so if that goes away, I'm gone.
Seriously reconsider this, or come up with a way to NOT crash the midgame economy, while not accelerating the lategame economy like you're worried about.