I increased and the gameplay is the same, nothing has been changed. I was trying several combination values, the last are:
SKILLS_SLIDING_TACKLE = 4000
SKILLS_STANDING_TACKLE = 4000
PLAYER_ATTRIBUTE_SLIDINGTACKLE = 5.0
PLAYER_ATTRIBUTE_STANDINGTACKLE = 5.0
In my opinion the levels in FIFA 11 and FIFA 12 are hardcoded in .exe and nothing You can change. In earlier fifas there were some ini files in gui.big and You can change easily tacking. I remember that in earlier fifas tackling was too easy.
It seems that Fifa 11 and Fifa 12 is like sex with Miriam. If You look at her she is gorgeous, You would like to **** her (Fifa has great graphic). But If You are in the middle of sex You see that she is transexual (has penis instead of vagina), You cannot **** her, get orgasm. The same way Fifa is. Gameplay is OK, but You cannot shot from a distance, You cannot dribble between two players, You lost with San Marino, the reality in the game is the same like Miriam is a woman.
Very poor designers in EA SPORTS.