Hm. That kinda sucks tbh. I guess once you’d beaten one siege you’d pretty much beat them all, but still a significant part of the fun was creating more and more elaborate defenses, with all the goblins dead and nobody to repel it seems like part of the game sort of dies. How about migrants? Are they more limited now or still an infinite stream of fresh cannon fodder.
If you don't use cheap tricks now it is quite possible to lose by attrition.
This is not true at all. You just need adequate diversity in your legendary armies. You can't just send out a squad of 40 wrestlers and expect them to beat 80 goblins anymore, but 20 axemen to sever limbs and cripple them, 10 spearmen for in case the axe men don't suffice, and 10 archers pelting down at them from a hill? You can certainly beat them, then. Cheap tricks ease the process, but it's entirely possible to survive without them.
To drive home this point, I recently had a goblin siege of 40+ goblins all on beak dogs. I beat them with 25 or so dwarfs, by luring them into advantageous terrain so I could not be swarmed and using a small group of archers to wear them down and kill their most dangerous units. There were many casualties on my side (most of them were poorly trained and not fully equipped), but I still won, with my 5 archers and about 7 hammermen (they were the only group with full armour) alive without permanent injury. The highest skill of any of them was adept. Imagine that with properly equipped legendaries.