The same at
The better DPS of Carbine actually means that is fires faster (around 18%) since both weapon do the same damage.
Pathfinders also get 2 carbine (with reckon getting one).
Allied squads do not have larger Target size:
conscript_squad_mp Target size: 1.09
volksgrenadier_mp Target size: 1
riflemen_squad_mp Target size: 0.97
grenadiers_mp Target size: 0.91
tommy_squad_mp Target size: 0.85
The critical kill mechanism should be a timed ability for all 3 unit and units with it should not be spammable.
Luckily, these units also compete against Elite units which usually have better Target sizes. Didn't use Obers as they arrive significantly later.
For PG/JLI .8
Using the mid range acc provided, Paths have good chance to hit with sniper crit
However, once light cover is applied their performance drops significantly
So about 1/4 shots to get that sniper crit going, as light cover is abundant at all phases of the game these numbers are the ones that matter most.
Now for the elites JLI compete against
Rangers/Commandos .73 combined both as there is only a .01 difference between the two
Shocks/Guards(Variants)/Paras/Penals .97 They are all between .95-1 so close enough
Midrange acc of .92 vs those target sizes
and applying light cover
So the one G43 outperforms the two Pathfinder snipers even in the worse scenario for the G43 which is going against Rangers/Commandos. Adding the fact that they fire about 20% faster as you stated would mean they are even as a worst case scenario for the G43.
At long range it is even worse as Pathfinders have between a 37-42% chance to hit elite axis units behind light cover. Where as JLI vs R/C have a little better than 75% chance to hit and around/over 100% chance to hit the other stated elites. The allied squads having 1 or 2 more models does not justify this difference in performance which becomes larger as both squads vet(Paths getting 25% acc and JLI getting 40%)
It also should be stated that none of the JLI numbers take into account first strike bonus and numbers are assuming that both units are meeting there threshold for the sniper crit which is easier for JLI.
In the end I do agree, neither should be spammable or at the very least like you said making the sniper crit a timed ability would solve some of the issue.