I think the game is actually easier to play on the hard setting. There isn't really much difference, but the few more groups of bad guys on hard make it easier for you to keep your guys attacking every round which increases their experience.
Anybody who has real trouble should watch the playthrough videos on youtube.
http://www.youtube.com/results?searc...mission+5&aq=f
You need to study the offered perks and choose the ones that fit your style. Definitely get any perk that increases experience. The difference they can make is huge.
It is much better to get gold victories on hard without losing any units, and that demands you study every mission until you've memorized the layout and locations of all the bad guys. I agree it is taxing, but it makes the inevitable victory more rewarding.
You're not going to win this game by accident.