I didn't misread it. The answer to "why do they attack offensive power of offensive units instead of their defensive power" is exactly "because Plarium decided so". If you're looking for their reasoning, we can only guess, because - as far as I know - the devs don't share that even with their own support.
The rest of my answer was just a bit of ridicule at the expense of some silly things in the game, nothing else. ;-)
HDB works but not on FS. Ye just have to invest enough in it.
One part of HDB that does affect FS. Scallies, Redcoats, and Gunner's Mates.
I agree that it is absurd to hit an offensive units offensive value with FS's. I might be wrong but I think it was a change later in the game made to help appease the anti-fireship brigade.
No, it was there from day 1, but it wasn't clearly explained. They said "Fireships hit 1 for 1 point" and we assumed that it meant "12600 def points". Only later did we realise that each unit has its points that depend on the unit type (off for off units, average of the 4 def scores for def units,...) and that "1 for 1 point" meant that.
HDB from haven guards has no effect. Only their off/def strength has (which one, though? I never bothered to find out, but I'd guess def).
this is true SEAGYPSY but you're talking logic this game has nothing to do with logic after all since when can you move an island, I realize there are politicans who beleive an island can tip over form being over populated but that is the same logic the game uses, they went to the same school.