My party has a ton of mercs and they're aligned in a long column of platoons of troops. Some rocs land on their tasty baggage train in the rear and the party starts to issue orders to attack the rocs. I point out that the column is a few football fields long and they can't exactly yell orders to everyone.
It's suggested that these are veteran troops and thus there's probably a system of signals in place like horns or bugles or what have you. I point out that there's a proficiency for that, Signaling, and none of them have it.
It's pointed out back to me that Signaling is used to communicate between signaling specialists and does that mean that every soldier needs to have it in order to understand basic commands issued by horn?
So I ask you, Autarch or reasonable facsimile of same, how is Signaling supposed to be used?
I don't believe every soldier needs to have Signaling in order to understand battle calls. I expect Signaling is meant for more complex communications across the battlefield - things more complex than "charge", "march", "ready bows", etc. Note that even in the D@W rules, Signaling isn't mentioned as a requirement for anything, nor is the proficiency itself even mentioned in either book. D@W:C notes that musical instruments and pennants are utilized for signaling orders, and that's about it.
I'd hope that the more general calls for movement/retreat/etc. would have been drilled into them as part of their formation training into Loose or Formed units (the signals necessary for them to know to operate as a cohesive unit), and perhaps witholding that basic level of training from Irregular units.
In your particular case, if I was being a stickler, I'd probably run along this train of thought:
Are the mecernaries hired all part of the same organized company, or sourced mainly out of the same culture (so they all fell out of one nation's army, so to speak, or any other socio-political reason for a set of signals to be common) so that their signals would be common amongst all of them?
If not, would someone have thought to agree on a standard singalling language and drilled that into at least the company/platoon commanders?
If not, then, how long does it take a runner on horseback or foot to run the length of the column shouting the order?
If they are all veterans, what level of situational awareness do they have that they may be able to anticipate likely orders and be prepared to execute? Bows at the ready to fire when the order is heard, shieldwall already prepping, etc? How many rounds would that take off the prep time?
If the party were to want to consisently execute complex maneuvers on the fly, I'd suggest that at least each company LT or platoon SGT would need Signaling and some time in training (perhaps someone with both Signaling and Martial Training?) to install the knowledge.
Not every soldier needs it. But someone trying to give commands at long range does, or else the person they're giving the commands to relay does, along with someone at the other end to receive them. If they were properly prepared, they'd ensure every reasonably-sized tactical unit had a signaller, and that they always had a trumpeter/drummer/whatever close by so they could send out orders.