Well, think of it this way. Going from the Mondragon to the Selbstlader M1916, you gain a detachable magazine that holds 15 more rounds in trade for only 32 rounds per minute. Going from the Cei-Rigotti to the Farquhar-Hill, you gain a detachable magazine that holds only 9 more rounds in trade for 42 rounds per minute and the omission of an automatic firing mode. So, I'd say giving the Farquhar-Hill slightly more damage than the Cei-Rigotti is quite alright. Of course, if DICE were to go through with the SLR range buffs, that may create some balancing problems, as you suggest, Shalan.
As far as the most versatile vanilla guns for each class go, I'd say the following.
Assault - Hellriegel M1915: This has one of the best close range TTKs in the game, and its low recoil will allow one to make hits at fairly long distances. It's not hard to see why this is one of the most popular guns in the game.
Medic - Mondragon: This is a bit of a tricky one. Medic seems to typically have the biggest trade-offs with each gun. While most generally gravitate towards the M1907 SL Sweeper or Selbstlader M1916 for vanilla Medic guns, they're pretty bad at long range and close range, respectively. The Mondragon has you covered for practically every range. Only true downside is you have to pay close attention to when you should reload (reloading with a single round left will take a while).
Support - MG 15 nA: It is has the best ammo capacity out of vanilla machine guns and thus is the most forgiving to miss shots with. The Lewis also has a respectable magazine capacity, especially on the Suppressive variant, but the long range damage is poor.
Scout - Gewehr M.95: It has a great rate of fire, great limb multipliers, and a consistent damage model. Once you get used to its lower-than-average bullet velocity, t's really a solid choice for just about every practical combat range in the game.