I have played a pretty good defensive tactic with arsenal for a while, but it is not suitable for them.
5 defenders. 2 stoppers and in the middle a cover. The cover should have good positioning while the stoppers preferably have good heading. The other two should be wing backs. Then i had a DLP in the middle to pass the ball to.
The rest depends totally on your team. If you have good attacking stats for your wingbacks, utilize those by giving them an attack mentality. Try to regain the posession in the midfield and then pass the ball to the wingers or striker(s). Counter works best for this tactic (especially if you are expected to end in the lower half of the league).