hehe, the problem with lurkers is that they can come in 5 minutes. IF you tech for tanks in that time, you don't have a good versatile army. If zerg dicides to go mutas rather than lurkers you are toasted. (zerg can very quickly chance directions, which is zerg's power)
Another issue is that good zerg players will not be taken by scan sweeps, they will make you waste sweeps on single lurkers till you are out of energy.
I have learned that all the many ways you can defend against lurker rushes will cause you to lose against zerg's flexibilty. You must keep yourself flexible and learn to beat lurkers with marines.
Carriers have the anoying habbit of comming into battle while you are very busy with ground battle against dragoons, zealots and templars. Then all of a sudden you have to swich to golliaths or wraiths to handle the carriers. Also do they attack while being on high ground where you don't see them and thus can't counter attack them.
DT's are dark templars. You see many beginner terrans doing very weird things to defend against these like building multiple bunkers with turrets. A sure way to lose.
If you are interested, i will gladly show you some of these things in reality on battle.net. Just send me a pm to make a battle.net apointment.
btw, with a mellee map with zerg and protoss you don't mean AI players do you?
If you practice against AI it is the standard to do so against 7 of them
