Beakons are a lot more versatile than you give them credit for. Maybe not for the shooters, but for snipers and close range weapons, beakons are a perfect distracting tool - a catch 22. If they kill your beakon, it wastes time that could be spent on the objective, and risks an ambush. If they don't, you or a teammate could ambush them at any time from then on. Since you're likely to be waiting around if you want to get an ambush, the ink hunger for the beakon doesn't matter much.
I'm less versed in snipers (read: can't aim for biscuits) so I'll start with that first. The E-litre and scope are powerful weapons which can one-shot from the other side of the map, so you can essentially act as a beakon anyway. This means that you usually don't need beakons down near your perch until you want to move out of position. Once you do want to move out, a beakon in a hidden place near your perch provides a good way to get back there, and gives a good counter to flanks for your teammates. Then you can chuck the other two beakons where your teammates will want to go, find a new sniping spot or superjump to the old one, and presto. Worth noting is that a beakon could probably protect you for long enough to superjump away, if nothing else. And again, they work well as bait if you can snap your shots, since it only takes one shot to kill and you can fill the ink tank while waiting for the enemy.
The Krak-On Roller and Octobrush work in similar ways in terms of beakons, and I main Octobrush and sub Krak-On so I really hope I know what I'm talking about. Basically, beakons let you organise ambushes, get teammates to key locations, and get between key locations on maps with more than one, like Port Mackerel Splat Zones. They aren't especially useful in combat (especially in TC since a sniper can shoot through them), but you really don't need a sub in combat if you're good with the main. For the Octobrush especially since it's faster, but also for the Krak-On, your first goal is to look at your team, see if there's a sniper, and if there is, get to a sniping spot that they aren't already going for, and place a beakon there for them. This gives them a wider array of options and can be a surprise early-game since usually a sniper would hang back. From there, it's mostly just placing them for ambushes, or to get back to the action when you trade.
