No I didn’t say that. The slower repair rate for siege is not a bug. And it makes sense to consider the mobile thing a siege unit rather than a building to make it vulnerable to attacks. Not only it is harder to repair but it also takes more damage from a lot of attacks than the building.
This is not true, it does increase but as I mentioned above in the “correction” it is not a linear relationship. See the vids below and check the HP change per second.
1 villager: roughly 5HP/s.
5 Villagers: roughly 16 HP/s. So it takes them slightly more than 5 minutes to repair the packed (5000 hp) landmark from near 0 to full.
12 Villagers: roughly 26 HP/s