How does one stay safe in being one of God's Seers here on earth?

It helps if you have good relationships with the Archangels if you are one of God's Seers on earth. Because everyone needs protection.

Why does God need people who are Seers here on earth?

Because the human race would have gone extinct hundreds or thousands of times already without them. 

So, whether they were shamans or priests or ministers or just lived their lives in a good way, God needed them to help save mankind from themselves for hundreds of thousands if not millions of years already.

By God's Grace