Is one's Midheaven visible to others?

Your Midheaven is how you relate to the world at large .. not socially, but in terms of finding your niche, your career, your calling.
Only in a professional (or celebrity) capacity will your Midheaven be apparent to others.

In astrology, each planet (including Sun and Moon) represents a different inner need, a different facet of your personality.

The Ascendant and Midheaven are not planets .. they are not part of your inner personality. They are different roles that you play in different situations. The Ascendant in social situations, the Midheaven in public/career situations.

Planet near Midheaven is most prominent.
It may stronger than Asendand.

It shows reputation, social standing, the career or "life path". It's our public face.

Our Ascendant shows our "Personal face".

Yes it is. It represents our career.
I have Scorpio midheaven 2' degree.
http://www.astrotheme.com/files/astrology_professional_destiny.php

Since your energy, your power of action, and your creativity are intense, you can be successful in the following areas: any occupation in the police and the military, miner, volcanologist, engineer, atomic scientist, scientific researcher, computer designer, surgeon, gynaecologist, sexologist, psychiatrist, psychoanalyst, dowser, astrologer, occultist, medium, clairvoyant, mystic, corporate manager, banker, financial counsellor specialised in stock exchanges or investments, funeral director, as well as politician leader.