Guild Wars 2

I’ve seen invaders, instead of knocking down the garrison’s water route’s outer gate, jump onto the ledge beside it and with a couple more jumps bypassed the outer gate completely and proceeded with attacking the inner gate.

Is this supposed to work this way? As a form of jumping puzzle to bypass the outer gate?

No. This is a terrain exploit and is blatant cheating. ArenaNet fixed one exploit but accidentally created a new one with their modification to the terrain.

We’ve had a guildmate ask ANet if it was exploiting, after it was done to us.
If i remember right, they said that it’s not intentional (so will likely be fixed over time), but it’s not exploiting since it’s simply jumping using the actual terrain.