After the raid leader finalizes groups, it's a good idea to discuss in each group who has what group abilities and then transfer group leadership to the person whose group leadership abilities will benefit the raid the most.
On most raids, we will have the raid version of Health of Target's Target - but if not, every group should make sure they have Group HoTT, because that ability makes everyone see whom their target is attacking. Having or not having HoTT makes a huge difference on raids.
The other abilities that can make a difference are primarily Health Enhancement and Spell Awareness. Most of the other ones are good too, but not as important as the ones mentioned.
The ability that noone should use on a raid is Group Delegate Main Assist. You want to know what monster the Raid Assist is attacking and not the Group Assist. Also, due to a bug, the Raid MA circle is sometimes not visible for people in the group that set Group MA circle - so you definitely don't want to have Group MA set in your group.
If you decide to use Group Mark NPC, be aware that it may be difficult to differentiate monsters marked by the group version of the ability from monsters marked by the raid version of the ability. Make sure this does not make the raid harder for other people in your group, and if it does, ask the raid leader to make some changes to the group setup.