do deploy gear effects like pillaged armory only affect the units on the battleifeld it was deployed on?

Radiance rules aren't published yet. This uses the printed card and current rules only, and it isn't a ruling on the new mechanics.

No — Deploy only governs where the gear is played (rules 149.2, 152.2). It doesn't restrict what the gear's other abilities can reach.

For Pillaged Armory specifically, the triggered clause reads "Buff a friendly unit" — not "a friendly unit here" — so the Buff can go to any friendly unit you control, wherever it sits, including at your Base. What is location-tied is the trigger: "when you conquer here" only fires if you conquer at the battlefield Pillaged Armory occupies. Compare Banner of Conquest ("friendly units here have Assault") and Portable Portal ("friendly units here have Ganking"), which do scope their effects to the battlefield — the difference is the word "here" on the effect, not the [Deploy] keyword.

This is my interpretation based on the printed Deploy reminder and Rule 152.2. No official FAQ exists for this specific interaction.