Have been using this formation for last 4 seasons as my main formation.
I play Normal-Mixed-Counter off-Hard Tackle-Zonal mark.
Down arrows on DMC and 1 MC.
I usually move 1 of the ST to AMC and put an UP arrow on him.
Have seen it being effective against 4-2-3-1,4-4-2,4-5-1V and most other formations.
The one that has caused me some discomfort has been 4-1-2-1-2ND.
But can counter that by moving Ml->AML and MR->AMR.

One of the main things for this formation is to have good heading attribute in your defenders and a Defensive Wall to take care of free kicks since I use hard tackle.