Take a chill pill ross. All you need is more practise cuz there's much more to learn in we8/pes4 then we7/pes3. The defensive features have been great for me. On 5/6* 10min I'll finish a 38 match season with the top defense record (approx. 20 goals against). I find 6* 15min to be too ez cuz I can beat a team like Chelsea 6-0 (lazy ai defenders). 10min is great and very hard just keep practising, it's supposed to be a challenge. Whater you do, avoid fifa!
Some defense tips:
When defending avoid using speed burst (causes inaccurate tackles + wastes stamina). Only use when you are really far behind. Get in range and hold X, you'll usually knock him down but it's better than him running away

. Slide as soon as he deaks pass you, but yellow card.
The square button is your life saver, press it to clear loose balls in situations you wouldn't think was possible, even uncontrolled players can clear once pressed. Don't toy around in your own box against teams with fast strikers.
You also need to use lots of tactics. Tall defenders/or good jumpers against tall strikers, fast man marker against fast and tricky strikers, etc. Also not a good idea to use a tired defender near end of match, like Montero often is.
In formation settings during a match, learn to use quick settings. It instantly changes your formation to several preset formations (each team has their own unique set), such as Defense Only when leading 1 goal late in game.
example, when leading fairly late in match with Man U against a good team, I'd switch to balanced. This causes the wingers to fall back alongside Keane and Scholes and create flat 4 midfield. Then sub 1 of them with CMD like Fletcher or P. Neville. This tactic usually takes away lots of space from opponent. Using Defense Only too early in game is not always good idea, you'll give up all the possession and they'll just keep firing away until eventually 1 gets by.
last minute tip. Try to avoid using blue arrow players (unless they're so much better than your green/yellow/red players), they almost always have slow reactions. Don't even bother using grey arrow players
This is the beauty of we8/pes4. You can't just go into a game and play. You need lots of planning. Practise and hopefully soon you can defend like me