Well, this could be thought for every class that is very effective, actually.
My biggest killing rampages so far have been with radiomen: The squad upgrade making arty cool-down 8x faster is really awesome, and allows to hammer the enemy repeatedly, and depending on map and situation, one can really decimate sometimes whole squads. in seconds, and do so every half minute.
Also MG squads can be very effective, again depending the situation and map.
Maybe a limitation really would make sense for such classes, like for tanks or planes, where only a very limited number can be active at the same time.