hello, 

i dont understand how a midfielder with low heading skill can have a good rating

In real life its one of the most important skill to control the middle of the field.

I checked many players and realizing this skill seems to be unless.

I need 2 good Midfielder for my team and i will considering to not look on Heading skill

and i can see many of managers dont training this attribute

What do you think about that ?

The match engine is not 100% realistic hence the discrepancies 

This is questionable... Pirlo, Xavi, Iniesta, Modric and most of the best midfielders use their head, of course, but seldom to hit the ball...