One, health and health potions. Your health gets eaten through so fast that unless you hide the entire time in cover or behind your shield you are screwed. On top of that you don't find many health potions, and that you can only carry one health potion at any one time till later svcks.
On to that even while in casual mode melee is worthless because enemies can easily stagger and overwhelm you with simple quick attacks. And not to mention range is iffy because of how much everything in the game blends together and the fact that enemies seem to be rather good shots so even popping out to fire can be risky. Add that with the lack of health and health potions, you can be screwed over quick.
And on top of all that the characters are rather uninteresting and as bland and random as the rest of the landscape and game. It is far to hard to get in to.