Lightning is too weak I'd rather use Rock Toss Godhand/Vacuum level 2 Paladin both do +70 damage to all targets Lightning only tops 40 damage and monsters even outside Dharma may survive 3 uses of Lightning they won't survive 3 uses of the other 2.
But before you do all that have at least 1 in the shepherd class besides I started the job grinding at level 12 to 15 and by level 24 I had Paladin already mastered by all 3 party members and had Whistle useable by all of them.
Btw since I freed the temple below level 15 I started the job grinding via Mt Cede as the "weakest" area however I could by level 24 either have Paladin mastered or have 50% of all the hybrid skills usable by all 3 pc's not doing both at once.
But when doing hybrid skill mastery ASAP for all 3 party members Lightning I learned towards the last 5% of learning them.
In fact the "quickest" hybrid skill learning ASAP method is to use the Strategy Guide faq on this site since it has suggestions for the best way to unlock all of them at once if you don't mind spending 10 hours of grinding to do so.
Well I still find Lightning worthless when 3 uses of Rock Toss/Vacuum will end most battles on disc 1 in 1 turn monsters will survive 3 to 4 uses of Lightning however.
When it comes to early level grinding I'd rather end all battles in 1 turn whenever possible and Lightning even outside Dharma temple won't do that the other 2 moves however will.
Besides that 1 faq that has a hybrid skill recommendation has learning Lightning itself towards the END of the hybrid skill leveling chain and learns Increase (and Whistle) at the same time as the very first moves.
I could either master all hybrid skills save the Sage + Teen Idol one in about 10 to 15 hours of grinding ASAP or master Godhand itself in the same amount of time.
At level 24 if I started to hybrid skill farm at level 12 to 24 I would have most Hybrid skills usable not just Lightning.