What Deadeye does is sidestep gameplay: it removes the target locking challenge and the maneuvering considerations associated with it and adds nothing in its place. Sidestepping gameplay is again not inherently bad: I'm sure you can think of an example of another upgrade that does so that I don't have any problem with. My argument is that the gameplay Deadeye removes from the game is not gameplay that should be removed: it takes something out of the game that it's stronger having.
Honestly I'd prefer not to feel like I need to use Deadeye to make my TIE Bombers work. I just haven't found another viable method yet. Guidance Chips help and are welcome, but are not sufficient by themselves because they don't solve the problem of how to get and use a lock in the early game. Only Deadeye and LRS address this. LRS comes with issues of its own:
1. It prevents the use of Guidance Chips (this is kind of a flaw with the "upgrade slots" model in general)
2. It telegraphs your target and makes switching difficult
3. It makes getting the second lock too awkward