I'm just wondering, is it supposed to be this hard to aim diagonally, am I doing something wrong, or is something not working right for me?

I can aim up or to the side without problem, but if I try to aim diagonally by holding the thumbstick in that direction, the aiming line auto-moves up or sideways and doesn't stay where I'm holding the thumbstick at. If I don't hold the thumbstick, but just tick it slightly in that direction, it works a bit better, but that's precision work with not that precise controls and it requires time that I don't have when I need to dodge bullets or charging enemies at the same time ...