I'm thinking specifically about the FD Ransacker here, since even disarmed and doing 0 damage he will trigger the 3 damage to support zone.
Teremus explained your philosophy, which is that basically 0 damage is still damage for all intents and purposes. I understand it's convenient from the designer's perspective for a few reasons, but an ability thats says it triggers off damage firing off off 0 damage is pretty counterintuitive (keyword here). The character I immediately thought about to kind of make sense of this idea was the Flame Ram, BUT! the Flame Ram is actually worded differently: "If Flame Ram directly attacks an enemy fortress, it deals 15 damage".
If anything, if the "0 damage is still damage" approach remains as it is, the wording on Ransacker should be changed for clarity. At least the Flame Ram does it right, and doesn't feel counterintuitive even to an inexperienced player.