Board Thread:Series general discussion/@comment-5088097-20170624223327/@comment-3535905-20170711091818
In conclussion (for those who dislike to read a lot, not me of course):
1- Eagle Vision is definitely a Precursor related ability and not a way of representing an Assassin's observational skills.
2- There are many types of Eagle Vision: Altair's (Default), Ezio's (available while running), Ezio's (mastered version also called Eagle Sense. It allows to "see" through time, watch past and future events". Also identifies the true nature of a person [Normal Eagle Vision cannot do this]), Connor's and Aveline's (identifies clues fast), Edward's (tag enemies), Shay's (tag hidden enemies and locates them), Arno's (short duration [who thought this was a good idea?]), and Frye Twin's (It evolves with practice).
3- It's not confirmed if Bayek possesses Eagle Vision.
The way eagle vision or the sixth sense is explained through the lore is that everyone has the tendency to unlock it but those with a higher concentration of First Civ DNA are able to use it without much practice. So, according to this Arno is said to have had a very low concentration of First Civ DNA compared to other protagonists in the series. This meant that he didn't have much control over it that's why he could only experience it in bursts and wasn't able to fully control it. About the assassination dialogues, Arno's low First Civ DNA concentration meant that he couldn't carry out full conversations with his victims but was only able to experience flashes of their lives. This, however, is not the case during Germain's assassination where Arno is able to carry out full-fledged conversations with Germain because of Germain's high First Civ DNA concentration.