The stuff in between square brackets are arrays, which is fancy programmer-talk for a list; and the thing about lists is that there can be more than one thing on them, so:
[soldiername1, soldiername2] join player
assumes the player is on his own or in command of his group - hence group player is unnecessary.
As for re-writing the whole thing, here's what I'd do:
1. name the player's helo, let's say chopper
2. triggers around the 2-man groups, give them names such as trig_grp_1. Make the triggers activated by the helo
(press F2 and then left-click-and-drag from the helo onto the trigger. When you edit the trigger, this list should read Vehicle, Group, Leader, Whole Group, etc. Select 'Vehicle')
once, present,
condition: this && ((soldiername1 distance chopper) < 10)
on activation: soldiername1 assignAsCargo chopper; soldiername2 assignAsCargo chopper; [soldiername1, soldiername2] orderGetIn true; deleteVehicle trig_grp_1
Make sure the soldiernames and trigger names are appropriate for each trigger.
3. place two triggers where the helo should land by the staging area, both triggered by the helicopter 'Vehicle' as above.
The first and slightly larger one should be: Vehicle, NOT Present, Repeatedly,
on activation LZ_Active=true
4. the smaller, inner one should be Vehicle, Present, Repeatedly,
condition: this && LZ_Active
on activation: LZ_Active=false; [] exec "disembark.sqs"
5. create the disembark.sqs script in the mission folder:
#start
_wherechopper = getPos chopper
_height = _wherechopper select 2
? (_height > 5): goto "start"
unassignVehicle soldiername1
unassignVehicle soldiername2
...
list all the named soldiers that are to be transported
...
exit
The scheme is:
the helo gets to the 2-man groups, and within 10 metres of one of the men (ie. is landing)
the two men are told to get aboard
whilst outside the staging area, LZ_Active is true
as soon as the helo gets to the staging area, the disembark.sqs script is run and LZ_Active set to false (to prevent the script running twice)
on getting down to five metres above the ground, the men are told to get out