[Marcov]

I'm talking about the Skirmish/Random map Mode of Warcraft III.

Still can't beat a single, easy opponent in a one-on-one battle! It's as if it were on Hard difficulty!

In the beginning of the game, I try and assemble and army, which I think is pretty big, until the enemy launches an attack with an even bigger one! 

After a long battle, the enemy always seems to have a stronger force.

Any idea how to beat the AI?? Anybody having a hard time on WCIII's Custom Game too?

[General Battuta]

No, WC3 was really easy (a lot easier than Starcraft). You're probably just not doing two critical things

1) maximizing your economy with a good early build path

2) creeping.

WC3 (to a lesser extent than StarCraft) is a game of map control. You need to be out there at all times, fighting creeps, getting levels for your hero. You should never lose a unit creeping. You should always scout the enemy's builds to see what he's up to and what hero he has.

Look up a good early build order for your favorite race and try to get it down.

[IceFire]

Some good advice there... also don't discount the huge difference that upgraded units and heroes make. I remember a level 6 hero could have a huge effect on a battle so long as their powers were used to good effect. But also those armory upgrades were very very useful. One upgrade only does a few extra points of damage per hit but in a battle it adds up big time. The difference between a large un-upgraded army and a smaller but upgraded to the max is in favor of the smaller upgraded one for sure. Especially in cases where you get a range bonus like on the archer or rifleman.

[General Battuta]

I recall Death Knight/Crypt Fiends being a good build.

[chief1983]

We played some custom games utilizing those traits as basically exploits.  Back in the old days of BattleTanks (custom WC3 game), you could upgrade your friendly creeps.  What we figured out was, if at least 3 people dumped all their starting cash into creep upgrades instead of tanks right off the bat, you could get creeps nearly as powerful as the hero units the other team was fielding.  It was hilarious watching creeps alone push back a team of creeps + heroes all the way into their base, while we sat back and leveled up.

[Nohiki]

Also if you're learning, find a more experienced player and do tandems 2v2, it is easier if you can defend together. I utilize night elves (1 mine/8 wood whisps/warden/6 archers for start), and it works well, providing enough wood to do all armor upgrades and stuff. The warden is imho the most powerful hero in the game, her fan of knives on higher level is capable of tearing down enemy workers to shreds with a single shot. Imagine what impact it has if you blink right next to a gold mine.

[X3N0-Life-Form]

Blizzard's RTS AI have always been (well, I haven't had the chance to test the SC2 AI yet) kinda ****ty. They would always build a powerful initial strike force and try to rush you, but if you manage to resist that, you have pretty much won.