It's still quite possible for a sufficiently buffed attacking army to wear down your city's defense if your army isn't hitting them back hard enough during the battle.

Watchfires also only impact your city army's defensive stats, not their attack stats, effectively hardening your defenses. However, Watchfires originally could not be upgraded and now cap at a 6% bonus - unlike Great Buildings which can, theoretically, be leveled significantly higher. Basil, Deal Castle, and the Terracotta Army. On a per-tile basis, Watchfires (and Ritual Flames) have an outsized impact over other defensive buildings such as the Monastery, the Athlete Living Quarters, or even the defensive Great Buildings, the Cathedral of St. With one or both Watchfires upgraded, they are 25-50% better than a non-upgraded Ritual Flame, but equal to a Level 2 Ritual Flame which only takes 1 upgrade. At 4% defense bonus two of them have the same impact as a Ritual Flame, but with the added placement flexibility of each only taking up a single tile. The Watchfire has many useful characteristics. The upgrade adds 2% to the Watchfire for a total of 6%. Its upgraded version will then be placed directly on the same spot in your city. To upgrade the Watchfire, use the Watchfire Upgrade item on the Watchfire that is already situated in your city. More detailed info can be found on the Great Building's page.The Watchfire can be upgraded by Watchfire Upgrade Kit item.

This table shows for each Great Building which levels are profitable for a higher level Arc (1st place only). Guild goods shown is for each type of goods in the player's current era.

Bazaar forge of empires