I've finally gotten around to playing adventure mode, and all of the random chatter between hill dwarves and townies has made me suddenly remember that something has been missing from my fortresses for a bizarrely long time. Despite all of the companions and random drunks imploring my adventurer to slay roc's, dragons, and hill Titans, in the nine months I've been playing this game, I have encountered two surface megabeasts in fortress mode, period. That was two dragons in the same fortress, back around 40.05. Since then, I have not had one surface megabeasts attack any of my forts. I've had countless forgotten beasts come up from the depths, sure, but when you know that every beast of any significance is going to arrive in the caverns it's really quite easy to install some drawbridges to wall any dangerous ones off indefinitely. Variety is the spice of life, and for all of their procedural generation the forgotten beasts have started to become rather dull to deal with. I've never encountered a roc, a bronze Colossus, a titan, or a hydra, leaving the surface of my forts worryingly benign.
So, what I want to know is whether or not other people have encountered a lack of megabeasts on the surface in the last couple of updates. Is it possible that some kind of bug is preventing them from attacking our forts? Have surface mega beasts always been less common than forgotten beasts? Or has everyone else been getting a decent number of surface megabeasts? Is it possible that there's something I'm doing at worldgen that causes fewer surface megabeasts to survive? I tend to go for medium-short history length (125-250 years) and meduim-high beast frequency. Also, does breaching the caverns early encourage forgotten beasts to spawn instead of surface megabeasts?