...station them somewhere...
...standing close to the spot...
...standing right outside the pillbox...
...stand miles from them...
...they station themselves "in the general area"...
These are all accurate descriptions of the current Move/Station behavior. 1x1 burrows work far better. If you want to get a rotation going, you'll need to do the following:
(1) Establish a squad
(2) Set up all of the 1x1 burrows you want for guard posts
(3) Establish an alert that is not "Inactive/Training"
(4) Under the schedule for that alert, give the order for Minimum 1 to guard the burrow you designated. You can, if you like, choose which dwarf you would prefer to take duty here -- this could be used to ensure that every two-dwarf watch has an axedwarf and a hammerdwarf, for example.
(5) Highlight the month you chose and re-select "give order" (not edit order!) and give another order, Minimum 1, to guard the next burrow. Once you give the order, verify in the Schedule screen that the blue text in the lower left says something like
Guard DoorPostA (minimum 1)
Guard DoorPostB (minimum 1)
(6) Repeat step 5 for each 1x1 burrow at which you want a continuous presence.
(7) Optionally, add an order to "train"; set the Minimum so that once guards and trainees are accounted for, two or more dwarves can be free to eat/drink/party. Verify that the text in the lower left says:
Guard DoorPostA (minimum 1, prefer 1,3,5,7,9)
Guard DoorPostB (minimum 1, prefer 2,4,6,8,10)
Guard DoorPostC (minimum 1, prefer 1,3,5,7,9)
Guard DoorPostD (minimum 1, prefer 2,4,6,8,10)
Train (minimum 4)
(
Copy the order and paste it to each month.
(9) Set the squad to the alert you established.