Joor, you haven't given us any real indication of your test methodology: did you go on holiday? Manage them yourself? .. or your results: number of saves, number conceded, average rating? .. and you've quoted a very small sample size (12 matches, only?) .. so I don't accept your repeated assertion.
Personally, I've always used
Concentration as a litmus test for goalkeeping - seriously, weighting it as high or higher than "Reflexes" and "Handling". And I've wound up with the Premiership's top-rated 'keeper that way.

So you'll have a lot of work to do to convince me that its meaningless.
Composure isn't just an attacking stat, either, the manual states
Quote:
| Composure: The player's steadiness of mind and ability, particularly with the ball. When faced with a big goal scoring chance or heavy pressure defensively, a player with high composure will be able to keep his head and more often than not make an intelligent decision which is beneficial to the team.
|
Why wouldn't that apply to goalkeepers, as well?
Similarly, Concentration notably applies to offensive players as well as defensive players, and I've certainly seen low-Eccentricity keepers appear to lose concentration in the 2-d highlights. What else would be causing that?