Can Mystic Eyes of Death Perception kill Tiamat?
Without a concept of death, Mystic Eyes of Death Perception are useless. They work on the basis that death is an intrinsic part of life, as a living being is meant to end at some point, the concept of death is already inside them, which is what the MEoDP bring about.

From Tsukihime Dokuhon PlusPeriod - TSUKIHIME Dictionary: Mystic Eyes of Death Perception [Unusual talent], p.184:


  "(...) Though they are said to see the form of death, strictly speaking it's more accurate to say they're reading the lifespan of a substance – the existential limit determined at the moment of creation(...)"


Tiamat, as a perfect being has no concept of death in herself for the MEoDP to see. You'd have to make her mortal first. For example with a Conceptual Weapon like the Black Barrel which imposes the concept of mortality upon its targets, Gun God uses it against the Types in Notes.