Having played both 2012 and 2014, I agree that overall stability and FPS has gone down in general. But in my experience, these things depend as much on play style, embark locale and other such variable factors, which can be controlled if you are mindful of them. Of course, this all gets thrown out the window during succession games because not everyone is aware of what to avoid.
Heck, that reminds me. We were supposed to floor over before building walls in this succession game to avoid the tree crashing bugs, but no one has observed this rule as of yet and we are still perfectly fine because not a damn tree
DARES to grow on the sacred ground of Murderflood.
Oh the cavern seal did come loose during my turn, I didn't do anything to tamper with it but I suspect it was the mudman as they are building destroyers, are ignored by the undead, and they got wrecked by the weapon traps
(which was how I was able to notice that things went wrong.)I did a test run of the game after Gwolfski's turn to try to isolate the FPS problems. I only played 3/4 of a season. Results may vary so take them with a healthy helping of skepticism.
I was able to recoup some FPS after getting rid of all the undead in the bottom cavern. FPS jumped from 15 to 25 at its lowest stable point. Allowing the magma dike to fill to max did not recoup any discernible FPS. Was not able to conduct test on other flowing liquids. There are multiple sources of flowing liquids on the map, including an isolated lake in the caverns, our own terrifying lake which does not seem to refill, the water reactors and the 2 pockets of magma on the level above the magma cistern that do not refill. I suspect the rock quarry also contributes towards pathing lag with all its open spaces and winding paths but have not done any experiments to confirm.
I'm not going to suggest anything, but these things might be helpful to know if we desperately need to optimize the fortress later on.