AR0305 doesn't have a default area script assigned, so you have the AR0305.bcs you created, but I suspect the area file idoes not reference it. You can add the script reference to the area file by adding this to your tp2:
COPY_EXISTING ~AR0305.are~ ~override/AR0305.are~
WRITE_ASCII 0x94 ~AR0305~
BUT_ONLY_IF_IT_CHANGES
Be warned, if you patch the area file in this manner then, use a save game where the area has already been visited, the change will not appear, nor will the NPC.
As an alternative, append AR0300 and move the NPC where you want them, instead:
IF
Global("F1GARTKExists","AR0300",0)
THEN
RESPONSE #100
SetGlobal("F1GARTKExists","AR0300",1)
CreateCreature("F1GARTK",[2100.3000],13)
ActionOverride("F1GARTK", MoveBetweenAreas("AR0305",[758.799],13))
END
Edit: Needed correction.