A Thunder team with Tyr and Sol will be viable with D'art's Discipline Relic weapon. But that's like 6 months out, almost as long as the wait for Mammon with the 3rd Miracle ticket (~8 months). Until then you need Raiko also, and are still lacking -DEF. Thunder's priorities shift over time as debuffs no longer become the main constraint. A final team with only Mammon and Sol should do just fine.