I find it hard to discuss people like The Endless in terms of battles. From what I understand characters of this power don't really tend to fight, they're order of power is just known. And i would guess that Sandman is above Loki.
Mind powers as in telepathy? Morpheus' only major TP feat I can recall would be planting dreams about the City of Focative Mirrors in Martian Manhunter's mind. Although Dr. Destiny drove the entire planet mad with just a portion of Dream's power, so I guess that should count in his favor.
The Endless are generally out of Loki's league anyway. That and the fact that Dream is supposed to be the abstract personification of the universal subconscious should make a mindwar between him and Loki a one-sided proposition.
Dream as every endless is dual aspect, as much as he is dream he also reality, and thus the most powerful reality warper. By default hes above Gods
Nothing is above God, the endless are faith powered entities a popular idea among fiction. They are much more powerful than gods because countless people across the multiverse believe in them as concepts not just a population on one planet.
Nekron the most powerful villain in the DC universe is another side of death, Neil doesn't like that idea but unless he changes that in the upcoming Sandman pre-equal it's canon.