I found it to be a waste putting points in Lightning Bolt. It's very weak compared to Jupiter Thunder. Sure there is a 2s cast for Jupiter, but that's what Wind Arm is for, reduction of cast time.
From observing Sorcerer in my party, I see that they constantly spam Frost Bolt until their target is debuffed by Wind Arm. Then, they spam their Jupiter Thunder until Wind Arm wears out.
Here's another reason. At Lv5, Lightning Bolt only dealts 22%, with Frost Diver or Wind Arm, that's 44%. For Jupiter Thunder, at Lv3, you dealt 64%, with Frost Diver or Wind Arm, 128%. That 2 second cast wait is totally worth it!
Earth Shield is primary before Deluge, healing is mainly your party's priest job. Earth Shield gives a nice boost in defence, in terms, you and the priest heal less often.