Ok, I'll take the bait on the What If (using the Whatever It Takes approach)
Hile Troy came from our world, and from the American military at that, so he had a great deal of knowledge about firearms.
Since he had several years in which to work before the onslaught of Fleshharrow, he should have worked with the Lords to build an extensive military/industrial complex to produce firearms and high explosives. Given the capacity of the Loresraat and the industriousness of the Lords, they should have had gun and ammo factories going fairly quickly.
A mandatory draft should have been imposed on all the men and women of the Land excluding the Plains of Ra (an independent people) and the Haruchai (also an independent people.) In any case, the Ramen had their own draft, and the Haruchai were bound by their Oath.
This would have increased the size of the Warward to over 3,000,000 strong, and the military/industrial complex would have seem them equipped with handguns, rifles, and cannon. Hand grenades, mines, and other personal explosives would have been ready.
Railroads (easily conceived of by Hile Troy) could have freighted the Warward to any part of the Land where it was needed.
Telegraph wires would have ensured communications (as long as they were guarded and repaired after attacks.)
It is even possible the Giants could have built Ironclads, which could have patrolled the Soulsease, Black, and Landrider Rivers, as well as threatening Foul by sea.
The use of high explosives could have rendered Landsdrop all but unclimbable, and the entire cliff face could have been rigged for hundreds of miles in case anyone tried an ascent.
Vast minefields could have been enplaced around Mount Thunder, and all through the lands both directly below and above Landsdrop.
Let Fleshharrower and his vast army try to ascend Landsdrop, when explosives are sending avalanches down to bury the climbers, and the booming of thousands of cannon are raining destruction down on his troops.
As for the rifles, the men and women of the Land were sharpshooters (see LFB, the bridge in Mount Thunder) and with rifles could have picked off targets in the Spoiled Plains from atop Landsdrop, in what would have been a massacre of Fleshharrowers' forces.
And, of course, even should Fleshharrower somehow break through the cannonades, the rifle volleys, the high explosives blowing Landsdrop apart as they climbed, the minefields behind, they would face a wall of guns (the Alamo on a grand scale, with defenders ever bit as determined.)
(chuckles ruefully) Lord Mhoram would faint in horror at the implications of these suggestions. After all, large amounts of timber would be required, and coal mines, and iron mines, and air pollution, and ...