ep1 was hard until i learned how to do the boss quickly!
ep2 and ep3 weren't a problem on normal, and i think it's fine on hard, it's just hard lol
haven't tried ep4 yet... long story why lol
i think it would be nice to give more time when killing the shamblers, but honestly, the fact that they don't add more time value makes it more exciting.
it's funny but makes sense that hard difficulty is easier than normal, haven't tried easy yet though