Basically, the formations looks a bit like this (image is the courtesy of FML-Tactics):
In some cases, the DM (defensive midfielder) is replaced by a regular MC (midfielder central), but this is pretty much how it looks. Depending on if you're facing a classic tactic or one created with the tactics creator, there will be some differences in the definitive setup, but this is the overal look of the thing.
Instruction-wise, these formations have one thing in common. They are ultra-narrow. I mean really narrow. What they rely on, is dominance in the centre of the pitch. Call it a glitch in the Match Engine or whatever, but playing very narrow upfront and in midfield seems to work wonders.
Your own narrow midfielders are perfectly capable of going wide to track an opposing winger, whereas the same winger or midfielder seems unable to cut inside to mark a run of the narrow player.
This generally leads to the three forwards overloading on the two central defenders, because the opposing wingbacks won't cut inside to help their centre-backs, unless you instruct them to man-mark, which most managers don't do by default (the default setting for most wingbacks is zonal).
When you leave a match versus a team like this to your AI, you're pretty much screwed. Your AI won't make the necessary changes and when it does, the other manager can just change his tactic around again and hammer you anyway.
Should you find yourself in a live match versus a 4-3-3 or 4-1-2-3, don't despair. You can beat them. I won't say it'll be easy and it definitely won't be a pretty match to see, but hey, it's not your fault they're all mindless sheep playing the same generic formation someone posted on the forums, right?
Taking in mind I'm using a 4-2-4 formation (basically a 4-4-2 with advanced wingers), this is how I counter the swarm of mindless sheep using the same formation.
First of all, my DR and DL are set to man marking. That doesn't mean just general man marking, but I assign them to a specific opponent. My DR picks up their FLC, whilst my DL picks up their FRC. That should leave my two centre-backs to deal with their remaining central forward.
That isn't enough ofcourse, as your defence will most likely still be spread wider than their offence, meaning your wingbacks still have to cut inside to mark their target, which they are generally not good at.
So the next thing we do, is change our style of play. I generally opt for a counter-attacking match strategy. This automatically narrows the own formation to match that of your opponent sufficiently to allow those wingbacks of yours to pick on those pesky all-speed winger-attackers.
As I said above, the 4-3-3 / 4-1-2-3 sheep usually employ very fast forwards, who can run at your defenders and skip past them. There's not much you can do about that, but you can limit the effective range of these speed demons.
The best way to do that is to use one of the in-game shouts. Tell the team to drop deeper. By dropping back, you effectively decrease the amount of space a forward can run into. More often than not, if a striker does run through your defence, he will find himself in a difficult angle or even running the ball out for a goal-kick.
Setting up your keeper as a sweeper-keeper also tends to help, as he can help sweep up any through-balls or pesky strikers chasing after such a through-ball.
That pretty much sorted out the defensive part of taking care of the mindless drones, but I'm quite sure none of you are satisfied with just keeping them at bay. No, we wish to punish them for their lack of imagination by actually winning the match or at least putting a few goals past them.
So here's what we do. Again, we look to use the in-game shouts. Since your own formation is by default wider than theirs, as you are using at least two wingers or inside forwards, your opponents weakness lies on his wings, where he basically has no players.
Sure, the central players will drop wide to get at your wingers if needed, but that will take time and we're not going to allow them that time. No, we are taking advantage of their Achilles' heel and we are hitting them where it hurts them the most. We're doing this by using the exploit the flanks shout, which does exactly what it says on the tin.
Next up is the get the ball forward shout. We don't just want to go wide, we want to go there fast, as we don't want to allow their central midfielders to drop wide and pick up on our runners. So get it out there and get it out there fast.
Last up is the pass into space shout. If your wingers start running with the ball in their feet, they're usually a bit slower, so let's not do that. Since the opposition has no-one directly picking up your wingers, they're going to have a fair amount of space, so let's use that to our advantage. Let the wingers chase after a ball that's not played into their feet.
More often than not, this will draw an opposing wing-back out of position as well, as he will try to intercept. When your winger is fast enough, he will usually skip past this wing-back, which leaves your man on the ball, plus your two regular forwards and other inside forward/winger on the other wing versus three defenders.
Sure, that won't always result in a goal, but in the end, you're always going to put a few of those chances away. Oh by the way, this isn't a 100% guaranteed way to success against a 4-1-2-3 or 4-3-3, but I reckon I've won about 80% of my live matches against one this way.