I think you should do whatever suits you best...
you have a choice, either be more accertive,
E.g, if a user deletes their own files then let the managaement know that it was the user who deleted their own files.
when they have a go at you just tell them,
"look it's not my fault he deleted his own files, that was his own stupidity, and now if they are gone, then they are gone. if he wanted them, then he shouldn't have deleted them. they are gone and there is no way they are coming back, it's as simple as that"
Believe me, that works... I saw someone delete an entire project once (when i was working at a software company). loosing a days work for himself, and meaning that everone else in the team was then basinv work upon code that hadn't been written yet...
He tried to blame me, even went to the MD, at the end of the day, the fact that he had deleted the files, and the fact that I was outwardly confident that it wasn't my fault meant that not only that he was to blame, but it also made sure that I wasn't to blame, and didn't get blamed.
and by more accertive, i also mean that you either have to accept the long working hours, that are in your contract, and only do those hours (within reason).
Or your second choices are to put up with it, or change jobs...
To be honest though, whereever you go there will always be poor management.
I work in a Uni now, (I'm a network support guy) and I do user support, there are several times throughout the day hen I am talking to (supposably intelligent0 people (i.e professors, and doctors masters etc)... who really don't have a clue.
If you let people walk all over you, then they will... if this is the case, then no matter where you go you're going to be in the same situation.