In scope of #2510, a "compromise" 3d optics variation was implemented. Personally, I strongly dislike it - because of the following reasons:
1.It creates a TrackIR cheat opportunity - if a player uses TrackIR, he can look to side, gaining "free" full-screen zoom
2.A reverse side of p.1. - such sights are hard to use with TrackIR
3.It looks unrealistic - the outside of the scope is also zoomed in
4.It creates bugs - like the bug with the DoF causing the reticle to blur or the sights misalignment
5.The weapon sway is much harder to compensate when weapon is swaying independently of screen.
To fix these issues, there exist a modset (TMR). However, many servers do not allow mods at all, or, sometimes, TMR just can't be used for other reasons. This creates inconsistent gameplay experience in different circumstances.
In my opinion, current "3D" scopes are misimplemented. I'd like to request revert of the "3D" scopes (RCO,ARCO,MRCO) to old "2D" type.