I love how people are lowballing the enemy stats by the way. With 0 modification, it has AC 36, touch AC 18. Saves are all 18 or 19. Not to mention, it has around 17k in loot, and armor is cheap as free.
My bad, I was looking at Unholy Aura as if the AC boost only applied against good creatures, but yes if you optimize the Devil's feats and gear at all he blows the PCs off the RNG even worse than before.
The terribly gimpy Warblade (and yes, any beatstick with only +20 to hit at level 10 is a gimp) rolls a 20 or misses.
I'm sorry, where is he getting all of these huge bonuses to everything? For his stats I assumed Str 22, Dex 14, Con 20, Int 14, Wis 8, Cha 8, but let's just buy him some gear. Assuming the game played with standard point buy his starting stats are something like Str 16, Dex 12, Con 12, Int 13, Wis 10, Cha 8. At 10th level he's got 49,000gp. So, he puts both his level points into Str and obviously has a Belt of Giant's Strength. Current wealth: 33,000gp. Let's say he's got a
+3 Greatsword now. Current Wealth: 15,000gp. Now let's give him a Cloak of Resistance +2, +1 Mithral Breastplate, and a +1 Longbow. Current Wealth: ~0gp. So, with +6 from his Strength, +3 from his weapon, and +10 from BAB that's actually
1 less than the +20 I arbitrarily decided he had. Oh, and those stats I assumed he had? Not even close. So that's 40 less hp than I thought. What am I missing here?
And ok, the Factorum finds and identifies it. He is promptly ROFLstomped. Regardless of whether the party then ROFLstomps the devil, he still suffers from scouting fail.
Meanwhile, what actually happened in the actual game is that the party proceeded together, the undead Cleric auto spotted the Ice Devil, and is also you know, a Cleric and not a gimp. Right now, it's about even, but I'm quite certain the party will win this one.
Oh, okay, so you say that scouting fails no matter what because there's no way that the scout can spot anything at all relevant, but the Cleric in your game auto-spotted the Ice Devil and would have still done so if he for any reason decided to scout ahead. So the PC who isn't even trying to scout could have easily scouted and not succumbed to AADS to provide the party with intel, but a character designed to do that scouting, no, no he would have died. Instantly and without any consideration needed.

All of the odds you listed in your mock run of that encounter fit the RNG nearly perfectly. Most things are 50% chances. Isn't that how it should be designed?
Um, the PCs don't have a 50% chance to do jack shit. The Warblade barely has a 50% to hit with one attack. The spellcasters have close to a 25% chance to even get to attempt to force the Devil to make a saving throw which he has about a 60% chance to succeed on. Unless, like my Warblade example above, I'm missing some crazy way to get amazing bonuses to their save DCs and spell penetration checks outside their normal wealth by level stuff.
-The Warblade takes a swift action to gain distance then charges, activating Leap Attack, Shock Trooper, blah blah blah. The Ice Devil ishas a 50% chance or lower to be dead.
Also, I know the whole ubercharge build is really common on boards, but how often does it actually show up in games? I've never played it because it's been my experience that a PC that has a 50% or better chance to automatically kill anything so long as he can hit it, well, DMs don't generally like this.
-The Beguiler drop a save or suck with a DC of 28, very doable at level 10, leaving the Devil with 60% chances of success.
What save or suck? And how is he getting DC 28 now? Let's assume he has Int 26, spending over half his wealth on a +6 item. That means with Greater Spell Focus he's got DC 25. I admit, I'm not an optimizer, so I'm sure there's probably something I'm missing here, but if he's maximizing his save DCs I'm sure his HP and his own saving throws are going to suffer for it.
-The Dread Necromancer can either slam it with a couple save or sucks, or maybe use an undead force. He's not an idiot and they're buffed well, they are able to damage the devil.
Again, Spell Resistance. How are you blasting through his SR AND having amazing save DCs? Oh, AND buffing your undead constantly so they are actually amazing enough to hit AC 40+ and plow through DR 10 and Regeneration 5 effectively?
It just seems like Sunic and camp are conveniently ignoring the numbers when they make arguments for why Scouts blow, and then coming back with really optimized numbers when they want to make arguments for why Team Monster is awesome. This seems especially true given my above Warblade and Sunic's offhanded comment that some random Cleric not even specced to scout auto-spotted the Ice Devil with something in the area of +45 to Hide...
Now, I'm sure someone will come back and try to make me look retarded (I'm not an optimizer, I've never said I was. I understand it's value, and respect those who do it, but, y'know, grats if you do make me look dumb with crazy shit here) with optimization methods pulled from a dozen different supplements raising the stakes to the point that we're not even looking at a Tier 3 game anymore, we're looking at a Tier 2 game, and then we come full circle to the point that Sunic only has relevant information to contribute when we talk about Tier 1 or 2 games.