I leave it on defensive (not ultra) to help defend against through balls, it's actually quite effective at doing so, more so with med/med full backs.
Why don't you give my 2 teams a try and see how they perform for you? I am dominating a lot with them at the moment.
You have to use the exact team though because as an example swapping Mariano for Alves is actually going to make you defensively weaker imo.
http://www.easports.com/fifa/football-club/ultimate-team/show-off?showoffId=k5dHsueznKKon:ps3
the only change I advise to that team is Gustavo for IF Melo if you want to save yourself 40,000 coins other than that keep all the players and the chem styles the same.
This is the second team which I feel is a lot more solid
http://www.easports.com/fifa/football-club/ultimate-team/show-off?showoffId=jsqmhV29nKKop:ps3
The only player I can think you could swap out without ruining it is Vucinic for Tevez or Balotelli but again I think he's the second best striker I have used in the game.
Play style;
Defensive to counter through balls.
Use the CDM's to break up play and pressure the opposing team or to double up on wingers, etc I use these guys a lot more than anyone else defensively.
RCAM - he is the crossing option, if you see space or a slow LB use the RCAM to bomb down the line and put in a cross, now a lot of people here seem to think there is only one type of cross, there are 4 in total and I really like to use the triple tap cross (smashed in low and hard), the number of own goals, tap ins and rebounds this causes is LETHAL, I do also use the other types of crosses depending on the situation.
CAM - he is there to link play, play 1-2's with and long shots as well as pressure opponents (both my CAM's have high defensive stats).
LCAM - he is there to cut in and shoot, link up with 1-2's and cross the ball should the opportunity present but he doesn't have the same pace as my RCAM's so it is not an avenue you should try and force with him, if the opportunity presents do it otherwise pass or shoot depending on the situation. Nasri excels in finesse shooting, Guarin excels at power shots to the far corner.
ST - Well rounded beasts with high passing, these guys are there to run onto through balls, dribble past a player in a one on one and quickly pop a shot off or head or tap in crosses as well as play 1-2's or play in CAM's, there passing is not to be underestimated.
Should the opportunity present itself where you cannot set up a goal but can win a corner do so, e.g. through ball to wide man, nobody in the box but he's through with a CB cutting off coming into the right position to score, just pop off a shot and win a corner from the save.
Hit a longshot to win a corner or rebound as well.
Corners;
If the opposition doesn't like to bring the keeper out, you will learn this after the first corner, then aim slightly (1 tap inward) towards the goal from the starting position, this means it should be bang on the or just outside the 6 yard box (the easiest place to score a header from).
Now before taking it look at where your players are and where theirs are, is their someone marking a post, is only 1 post marked (usually only 1 is or none), then aim your header towards the other post after you play the ball in.
Hitting the ball; you want to aim for half power or slightly more with top spin, this keeps the ball moving fast (hard for their keeper to react) and low so it doesn't take ages for the cross to come in and them to get a player into position to defend it.
Other than that try and switch wings with a long high ball or play long through balls say from LB to RCAM whenever your pinned in, not only does this get you out of trouble, you can do a quick counter attack and sometimes it lets the RCAM clean through where their pace is unstoppable.
Other than that try actively not to concede, if they cannot score they cannot win, stopping goals is crucial.