So railway and telegraph lines might be a bust right now. But what about towers using morse code - they won't require anything connecting them inbetween - and depending on how theyre made they'll have a good range, quick info delivery, and magic and/or runes could make them safe.
I could invision telegraphing towers dedicated to let say Verena might allow for fullproofing (If the operatörs can identify the flashing light being verified Verena_telegraph) from chaos/evil. With the added bonus of eventually creating worshipboost from all the message flying everywhichway! 🤔😁
GNU Terry Pratchett
Actually the problem there isn't chaos, anymore than the mail service potentially being operated by chaos cultists would be.
The problem is
cost.
Lets list out what a heliograph tower requires to function:
-Up to three literate men for continuous uptime, two if you exclude nighttime functionality.
-At least two armed guards to secure the tower from gribblies and bandits, assuming sufficiently solid construction that direct assault doesn't happen.
-Food and water for all of the above, many of which would be far from civilization and require regular supply runs.
-Personal amusements and minor luxuries for the crew, lest they go insane the regular, non-chaos way.
-Either maintaining a constant supply of good quality fuel as per a lighthouse's beacon, or increasing the number of needed towers to transmit a message over a given distance of open ground. Note you cannot just harvest wood from the forest - green wood produces smokey fires which would ruin the next item on this list.
-Optical equipment necessary to discern and transmit a message clearly. Spyglasses aren't cheap, nor are large reflective pieces of metal, but without them you'd be again raising the number of towers needed substantially, which would cost you in food, water, fuel and pay.
-Towers must be constructed of sufficient height to reach above the treeline. The Empire is packed with old growth forest, this would be challenging, especially when using stone would be expensive, far from civilization.
The Roman Empire made use of such in favorable geographies, they even had a neat trick where connected water pipes let them communicate between towers by raising and lowering the water level in a siphon where the geography made line of sight hard, but theres a reason the practice ended when it did.
How many can afford to pay the logistics expense of such towers for the sole purpose of communicating more quickly? Even if the towers ran at maximum throughput all day, every individual message would be costly.
The main difference is that you can create Helstorm Rocket Batteries vastly more easily, quickly, and cheaply than you can an Archmage. And, really, you can totally kill 2000 soldiers in one salvo with Helstorm Rocket Batteries--you just need enough of them.
More importantly, you can't counterspell/dispel artillery, nor is artillery subject to the whims or conditions of the Winds of Magic.
Of course, the true Chad uses both battle magic and artillery. As we saw in the campaign for Karak Eight Peaks, using them in combination results in some pretty spectacular kill counts. Even the one major battle the Karak Dum Expedition had showed the value of artillery in combination with battle magic. By letting the cannons focus on major damage dealing, the battle wizard can instead focus their efforts on debuff/buff spells to help the melee troops win their battles on a large scale.
Well, artillery of the era was notoriously finicky to bad weather and terrain as well. I kind of suspect the wizard explosion rate over a campaign might actually be favorable to the artillery one - though on the other hand its much easier and quicker to replace an artillery piece than a battle wizard, and the consequences have a smaller maximum radius.
