Why do almost all overwing exit slides open over the trailing edge of the wings, and almost none over the leading edge?
The special cases you listed (minus the very special case Concorde) hold the clue.
The Il-62, DC-10, and MD-11 are all tail-heavy due to the tail-mounted engine(s).
The emergency exits are designed inside-out, not outside-in, meaning, the locations are not only dictated by each exit's size, but by the cabin's seating arrangement first.

(e) Uniformity. Exits must be distributed as uniformly as practical, taking into account passenger seat distribution.
(...)
(4) For an airplane that is required to have more than one passenger emergency exit for each side of the fuselage, no passenger emergency exit shall be more than 60 feet from any adjacent passenger emergency exit on the same side of the same deck of the fuselage, as measured parallel to the airplane's longitudinal axis between the nearest exit edges. (14 CFR § 25.807)

The tail-heavy examples by design have the main wing more aft, leading to that scenario. The rest, the opposite.
The DC-9 extended family[a] is more special, as there's an exit in the tail (also usable for entry):


Source: aircollection.org

And with the floor-level exits right ahead of the engines being not full-size (compared to the forward doors), it's been balanced that way. Otherwise it would have used an exit arrangement similar to the Il-62's, or the Vickers VC10 with a large exit forward of the wing in some configs, and/or over-the-leading-edge overwing exits in others:


Different VC10 configs; sources: wikimedia.org and wikimedia.org

The A310's reason is the original A300 fuselage that was shortened. If there are other configs, it would be related to passenger capacity.

a: optional on DC-9, standard on MD-80/90, removed from B717[1]
1: Becher, Thomas. Douglas Twinjets: DC-9, MD-80, MD-90 and Boeing 717. Crowood, 2002.