.50cal has a narrow arc and a very slow rate of fire. I find myself retreating this MG every time because its really easy to fight off. Now with the MG42, the gun has an excellent rate of fire, largest arc and not to mention a superb vet ability! You have to put a little effort into the MG42 when the Rifles are not being suppressed within the arc, just make sure to change the target to the unsuppressed squad.
the rate of fire is fine for the amount of damage and suppression it does.
if you use the M2 as a backbone for several rifles, and particularly with grenades, it won't take much damage and can stay on the field for a longtime, particularly with a major/ambulance.
again, rate of fire is not the be all end all and only acts as a modifier to the suppression and damage. the MG42 does have a huge arc outside of buildings but the poor traverse means it can effectively use all that arc in most situations. the maxim has a tiny arc but doesn't have any problems because it resets so fast and doesn't give a shit about suppression/pinning.
incendiary ammo does give the MG42 a huge amount of damage against infantry and vehicles but it takes forever to go off and sprint on the M2 allows for very fast repositioning and kiting. sprint is by no means a bad vet ability.
the MG42's ease of use depends on the map. this is true of all HMGs. both the maxim and M2 are easier to use than the MG42 because they don't care as much about positioning.
as far as HMG rankings go, i order them maxim>M2>MG42>MG34. i'm not going to include the kubel because the only similarities are suppression.