If you want to create a group of AI units you have to use createUnit for each single unit to do so.

It would be nice to have a createUnits command which can take an array of class names or a CfgGroups class and return an array with the created units.

Examples:
_newunits = group createUnits [["B_Soldier_F", "B_Soldier_GL_F", "B_soldier_AR_F"], position, markers, placement, special];
or
_newunits = group createUnits ["OIA_InfSquad_Weapons", position, markers, placement, special];

It would also be nice to have some kind of init parameter, code, which just runs locally on each created unit:

_newunits = group createUnits ["OIA_InfSquad_Weapons", position, markers, placement, special, {_this unlinkItem "NVGoggles_OPFOR"}];