You have to look for high grounds with the unclimbable barrier. The tower is not one of them, and you should only snipe there when your team has taken the turf around it, or you can try to claim it yourself by shooting short bursts in a circular motion. Never aim down when claiming turf, because the ink only travels the farthest when aiming forward. Since you can't see what's below you when doing this, look at the map to see if any enemies appear where you're inking and hide in the wall of the tower if you see anyone approach(or just bail).
Don't give away where you're aiming. Start by charging your shot above, below, or behind your opponent and gradually bring it closer to them so they don't see your laser. If you're on high ground, back up from the ledge so the lip hides your laser and just jump before you shoot(charge your shots behind walls too if you can)
In BBS, there is a pair of walls with the unclimable barrier. There's not much room to move around, but it's safer than the tower.