One thing that is bugging me at the moment is the way your centre-backs stand so far off the attackers they're marking; it makes setting up a tight and disciplined defence impossible. Unless the defending side can constantly block the passing lanes with their midfielders, which is very hard to do even some of the time (more on that later), the attacking team can easily slide passes into the strikers' feet while their markers back off and allow them space to turn. - unrealistically so.
As the manager of the team I should be able to instruct my players how tightly to mark off the ball. I've tried man-marking, I've tried High defensive work-rate, I've tried nudging the positions in Edit Formation, I've tried the offside trap... it's just something built into the AI this year.
The other thing bugging me is that the effect of inertia feels too strong now. Players stop, start and change direction much more sluggishly than in 09. I'm sure everyone has noticed how the LB 'stop dead' move is much less effective than it was in 09, an obvious example of increased inertia.
Defenders under AI control are more easily pulled out of position because they can't change direction quick enough. This is another reason why maintaining a tactical & organised defence is impossible, you end up with AI teammates motoring headlong in various directions and it falls apart clumsily.
Increased inertia exacerbates my first point about the strikers being given too much room. Denying the supply into their feet becomes more crucial than ever, but that task is more difficult than ever because your midfielders have a harder time changing direction to stay in those passing lanes, even using the jockey button.