Effective use of Assist Skills can give you a big advantage in a fight.
Many Assist Skills have a huge effect on tactics during a fight. For example, there are skills that can grant an extra turn to allies who have already acted or can support allies by buffing their stats!
Rally skills are wonderful, aren't they? When an ally uses a Rally skill on me, I feel even more powerful than usual!
I'm going to rally behind you too, Commander Anna! You are the heart and soul of the Order of Heroes! Your skill with an axe is unparalleled! I love your hairstyle! And you love money way, way too much!
Sharena... I was getting all fired up until you cut me down…
Great Assist Skills, Part 1
In addition to skills for inflicting damage on foes, there are also skills that give you a strategic advantage by assisting you in battle. Some particularly useful skills are Dance (Olivia, Ninian, etc.) and Sing (Azura), which grant an extra turn to Heroes who have already performed an action.
Great Assist Skills, Part 2
Other useful skills are Rally Attack (Sharena, Raigh, etc.), which temporarily buffs the Atk stat of allies, and Rally Speed (Seliph, Gaius, etc.), which increases the likelihood of follow-up attacks. Reciprocal Aid (Donnel, Matthew, etc.) lets you swap HP with an ally, thus aiding allies who are acting as tanks.