In WC/SC when You tell 20 troops to go through a tunnel, they will go around, as soon as the first units block the tunnel [happens in WC1, WC2, SC and WC3 for sure, i checked that out a few days ago]. Some will even stop half way. A simple solution is to tell the unit to wait, when the unit blocking the path is on a move to a set destination. So, if Unit 2 is following Unit 1, and Unit 1 block the path, Unit 2 should stick to Unit 1, and if too close, wait for Unit 1 to move a bit, all by checking if Unit 1 is moving in the same direction.
The reason i replied to Your post in the first place, is because it's a bug/feature that's in Blizz's RTS games since WarCraft 1 [yeah, i've been around that long].
Right now, i'm finishing up the Orc Campaign in Tides Of Darkness [playing on the up to date Battlenet edition of WC2] and the problem with path finding is the all the way. And in WC2 You could only select up to 9 units at a time. And just today, i was defending my base from a Paladin/Knight/Ba;lista mix with 3 Orges and 6 Berzerkers in one group. The Berzerkers got raped, and the Orges decided on NOT attacking the enemy after losing their way. So i decided to check that out again, and found out that the Orge units had to cross a 'stream' of Peons working the mines, and then travel through a small tunnel between a forest and a Turret, and they just couldn't handle it.
But it gets better, in one of the first Orc missions, where You must free an Axethrower and then lead him to his encampment. After uncovering the path to the camp, i created some additional units just to be sure the Axethrower will be safe. To my surprise, the units from my main base couldn't find a way around a big forest, and ended up stuck halfway, looking at trees. Yes, it's that bad.;]
The problem becomes even funnier after playing around in SC2, where similar bugs/features still exist.
Then call me an expert blocker. ;P Try maneuvering units between sieged tanks.:P
The sh..ty Reapers loved to block on a ledge, refusing to jump down from it, dancing around, and once every while, one reaper would jump down. Also, tanks in a condensed group had some problems. SC2 had most of it done better, but still, the problem exists. ;)

Some users experimented with some maps of their own and found out that both enemy and ally AI is quite impressive (without scripting). Here's an example. http://www.youtube.com/watch?v=uWYlMC8z0G8
And even in single player, the ally AI does some impressive things (like a resistance fighter taking care of the flying cameras while we're taking down a strider) which are done without scripting.

Nice video. :) Maybe I am wrong, but to me it always felt like what happened was always supposed to happen.

While certainly not perfect, StarCraft 2 has wonderful pathfinding when compared to other RTSes.

Well that's good to hear. I remember getting frustrated with the path finding in the original StarCraft, so that's good that it's improved (after 12 years, it better be improved!).

Remember the AI on the original Command and Conquer: Red Alert? That game frustrated me for most of my childhood with that AI system. Anyone who has played knows what I mean, you have BARELY 2-5 minutes before you have a huge army attacking you, basically forcing a wall of tesla towers just to stay alive xD

Then you have the otherside of HL2 AI
[url=]http://www.youtube.com/watch?v=e0WqAmuSXEQ&feature=related[/url]

To be fair, that's more of an oversight than bad AI.

exactly not an AI fault but programming fault. The combine just cannot see you.

FEAR uses a method of making the AI seem super intelligent even though it isn't and is VERY effective. I don't think a shooter has topped it yet.

I've played the game, i know what it's capable of, no need tor hype movies.;)
[the player is sh.t ;P]
Oh, and :
http://www.youtube.com/watch?v=jA2epda-RkM ;)

The AI in every blizzard game cheats, even in SC2. The insane AI in SC2 even has extra income pr. harvest and can perform actions with no delay. The AIs in earlier games, like Starcraft:BW have cheated by "knowing" the map, thereby knowing what you've built and where, without the need to scout it out first.

like everything else with this game i was also disappointed with it.
my whole strategy was based on hiding behind corner and shooting everyone in slow mow.
AI never flanked me and the only real threat was the invisible fast guys. who weren't smarter than fast zombies from HL2 (well almost. they tent to jump to sides from time to time)
so yeah.