I believe DEEPLY in the concept of eternal, saving ordinances, but I see them as "necessary" for US - a physical, visible, tangible token or sign of our determination and faith - an outward manifestation of our inner commitment. I believe they are necessary not for some checklist in the Book of Life, but rather to put our actions in harmony with our feelings and beliefs - to marry the physical with the spiritual in a real way - to embed our beliefs in practice - to be true "fruits" of our faith.
Does getting dunked in water miraculously cleanse me? Perhaps and perhaps not, but I KNOW it gives me an actual, physical experience which I can "remember" - that can form the foundation of my attempts to model and emulate and become like Christ. Likewise, does my getting dunked miraculously cleanse someone else? Perhaps and perhaps not, but I KNOW it gives me an actual, physical experience which I can "remember" (especially through regular reenactment) - that can keep me focused on humbly and symbolically bringing to pass the immortality and eternal life of man - that can keep me from the natural arrogance of focusing strictly on myself.