Unfortunately if your savegame is corrupted by a game crash there is very little that can be done about it… There are no online server based copies of your saves - this is only coming with the multiplayer update - for now, everything is local to your machine.
Steam Cloud can also cause additional problems as it can inadvertently update the corrupted file to the cloud - thereby stopping you from retrieving a good version from the cloud… Steam has no way of knowing that a savegame is messed up - it just tries to sync the latest files - and sometimes this causes more problems.
The _temp file in the Saves folders are the simply the last save the game was able to make - if you look at the datetime stamps you can see that they are very close backups so sometimes both copies are messed up - it all depends on what the game was trying to do at the moment it crashed… Sometimes you can replace the active savegame with the _temp one (simply renaming to swap them out) but sometimes this doesnt work either.
The global data file is the one that saves the stash, gold, forge items etc… it is common for all saves in a particular format of the game - shared stash, single stash etc…
This problem “doesnt still exist” - its a side effect of the beta game and any instability issues - i.e. the problem is not with the savegames, its with the game crashing while its accessing the savegames - for whatever reason. For example, just alt-tabbing away from the game while waiting for the character screen to load can sometimes cause a crash and this can then mess with the savegame files.
The only current way to ensure that this doesnt happen catastrophically is to make your own manual backups of your saves & filter folders… This will ensure that the worst that can happen is that you lose a single playsession and not your entire character or stash. Personally, I also disable Steam Cloud… just to make sure that it doesnt copy a messed up file by mistake.