I can understand the Stragus' original position. DF isn't the same game as the one that inspired the "Losing is ‼FUN‼" motto. Many bugs have been fixed, and the UI has improved (really, it has!), making it much more survivable. It's now very easy to create a fort that will never fall.
There is a pendulum of difficulty here. When the "Losing is ‼FUN‼" motto was coined, the pendulum was way to the difficult end of its swing. Now it has swung towards the easy side.
Goblin ambushes never seem to happen (although I'm going to try the fix posted earlier to turn them back on - thanks for that, Robsole!), and the sieges are quite a bit easier to deal with than they used to be. Part of that is that it's now much easier to get a decently trained military without resorting to danger rooms, something the user community asked for and Toady delivered. But part is also because by making ambushes and sieges come from the population of the attacking civilization instead of just rolling some dice and creating them out of thin air, Toady unintentionally made it much harder to get strong attacking forces. To make things tougher, he'll have to make changes to worldgen, which is a very complicated, chaotic process, which will make it very difficult to get balanced. It's likely that some worlds will have extremely overpowered goblin civs that can send a thousand ambushers the first winter, and some worlds will have no goblin civs strong enough to send anyone. The more complex he makes things, the harder it will be to get consistent balance. But Toady does seem to care about keeping things interesting, so I expect he'll work on getting the goblins a bit more challenging.
Tantrum spirals also just don't seem to happen any more. I've yet to see an unhappy dwarf in the new release series, and I hardly do anything to keep them happy. No mist generators, no engraved bedrooms, unsmoothed dining halls full of modest quality stone furniture. I've gone years before setting up any temples, and have yet to make a tavern. Yet still they're inexplicably happy. In earlier versions, they'd be brawling in the hallways. This is another place where recent changes have swung the pendulum a bit too far in the easy direction (in my opinion, of course). I expect Toady will continue tweaking the emotions to make things a bit more ‼FUN‼ again.
In my opinion, the game has gotten too easy, lately. Yeah, it's certainly possible to set up challenges. For my latest fort, I looked for an area with no metal ores and minimal trees, near goblins and a tower. This will make trading matter, since I'll need to import metals and wood. I'm also making a rule that there must always be an open path into the fort (no turtling), and no weapon trap may have more than 1 weapon. I still don't expect this to be too difficult, but it'll make things more interesting. The fact that I started in a world that had already had a fort also made it a bit interesting, since I retired the other fort in early autumn, so the new fort started in mid-autumn, and winter came pretty quickly. I'm really hoping I don't get a siege this early. My one, bronze-clad axedwarf and 2 stonefall traps don't make me very confident. :-/
But it used to be that you didn't have to set that sort of limitation to make things a challenge. I don't get the impression that Toady intended to make things easier, it just seems to be that a number of recent changes have had that effect as unintended consequences. I'm fairly confident he'll get the pendulum swinging back the other direction at some point.
Regarding the dwarven battle mentality, on the other hand, don't think of it as a broken AI, think of them as battle-crazed berserkers. The moment they see an enemy, their vision turns red and they forget all discipline and CHARGE! KILL! KILL! KILL!. Now, if you realize that that's the sort of troops you're dealing with, you can design your defenses around them.
You want to have your troops stay back until the enemy advances well into your courtyard, and then attack? Don't expect them to just stand there and watch until the enemy is in just the right spot, because they won't. Put your dwarves in rooms on either side of the courtyard, with raised drawbridges separating them from the courtyard, with pressure plates in the courtyard that will lower the bridges when the attackers get to the right position. Now they can't see the enemy until it's time to charge in.
Your dwarves should be set to defend burrows in the waiting rooms so they'll go there and stay there until they catch sight of the enemy (which won't be until the drawbridges go down). Yeah, the UI for setting this up is painful. You have to define the burro(w)s, then in the (m)ilitary->(a)lert screen you set up an alert and then a (m)ilitary->(s)chedule that has them defending the burrows for that alert. Then when the siege shows up, you go to the military->alert screen and set your squads to that alert. It'd be so nice if the (s)quad screen allowed you to specify a burrow, like it allows you to station them at a point (which really means somewhere near that point, but maybe in the courtyard, not the waiting room).
Don't say that the game is too easy, then ask for dwarves that are easy to control.
The dwarven mindset is very much a part of the challenge. They're not little robots in a computer game that will do exactly what you tell them to do. They're little drunken maniacs that you can ask to do things, and usually they'll get around to it when they've had a good drink and maybe a nap. And if you're lucky (and careful), they'll actually show up at the battle wearing their armor!