Summoner
The main focus of the new Summoner abilities is enhancing the strength of the Summoner itself, not the Egi pet. For direct attacks, the new actions "Ruin III" and "Tri-disaster" (the existing action has been renamed as "Tri-bind") will be added. Tri-disaster inflicts Bio, Bio II, and Miasma at the same time, so it should be quite important. The biggest new action, though, is the consumable "Bahamut Aether," which is granted by consuming Aetherflow.
The "Bahamut Aether" buff has the effect of increasing magic damage dealt, and allows you to trigger "Dreadwyrm Trance" when you reach three stacks. With the effect of Dreadwyrm Trance active, you can activate a highly damaging action. Thus far, the uses for Aetherflow have been pretty fixed, so this will force you to put some further thought into it.