Mandukya Upanishad says that: Samadhi and sleep are identical.

Yoga helps the yogi by giving him the feeling that the world is not worth bothering about, it detaches him from world; it makes him treat the world as a dream, i.e. an idea. It does the same to his ego to some extent because he becomes indifferent to what happens to him. But this is only feeling, he feels these things only but does not know that the world is mere mirage. Such knowledge can come only after soul-centric inquiry and reasoning and in no other way. That is why yogi cannot be Gnani. It is the difference between egocentric and soul-centric knowledge.

Yogic experience is based on individuality. Individual Feeling or opinion   that the world is unreal may change in future because all individual emotions are liable to change; and the fact is that individuals do change, as when they indulge in circumstances of practical life within the practical world   and they lose their sense of world unreality though previously they felt it. A permanent view of world as unreal or illusion can come only after soul-centric inquiry and reasoning; such knowledge cannot change.

Were one is sharp enough to grasp   he could discover the  fallacy of the three states  by soulcentric  reasoning alone and then it would not be necessary for him to have gone through yoga practice at all; that is why  yoga is for dull or middling intellects.

To know whole truth, you must know all the three states, otherwise one gets half-truth. One has to inquire in to the world that   confronts him. If one drops the world confronting him means it is his   incapacity to do deeper self-search.

On  standpoint of soul, the innermost self, Visions and Samadhi are  part of the illusion

Mandukya Upanishad  says  that:  Samadhi and sleep are identical.

 Brihad Upanishad does not advocate Samadhi. 

  In non-duality, contemplation has no meaning.

Sri Sankara says: - Yoga is not the means of liberation (page 132-133 - Commentary on Brihadaranyakopanishad.

One cannot get rid of ignorance through Yoga,  because yoga is practiced on the false self within the false experience.  Without getting rid of the ignorance, the  false self (waking entity or ego)  and the  false experience (waking experience or universe) will prevail as reality.

Those who are practicing yoga for long years and found tit it to be inadequate and useless to realize ultimate truth or Brahman   should drop yoga and  take path of wisdom in order to acquire Self-Knowledge or Brahma Gnana or Atma Gnana.