I think this may be a mechanics issue actually. So in addition to your chance to hit (which is 30% + ballistics skill [BS]) which can cap out at 95% you also have things that will hamper your ability to hit things. Low cover provides a 30% chance to dodge and full cover provides a 60% chance to dodge (in both cases by having it hit cover). This is on top of any other existing dodge that the person you're shooting at may posses (certainly an issue fighting against eldar).

To counter a person's ability to dodge you either need skills that allow you to break through cover OR you need skills that reduce your opponents chance to dodge (operative and assassin both have these in spades). As a result of actively trying to shred my opponents dodge my sniper build misses shots so infrequently that I am legitimately surprised when it happens.

Hope this helps!

You can use toybox to make it so your parties attacks never miss if you so choose.