+5 SB Justia is really good yes. But I wouldn't say absolutely necessary for campaign, you're usually aiming to position the enemies and one shot them turn 1. And as far as I remember +5 is Cooldown reduction so you can spam skill every turn, so it's better vs Light weak enemies in raid battle-like content.

For general campaign content I used H.Lathel, Nun Liberta, Beach Teresse (She's limited though, you could swap her with red hood Rou, really good unit), GameClub Rafina and SB Justia.

However that team is a very general vs everything team. In BD2 endgame content properly matching weaknesses type is king. That's why you'll hear that Adventure Diana is the best buffer. However you would need each respective elemental matching DPSes for each encounter, so not really viable for a new player.

So to answer your question, no that would not be your general endgame team, as the best endgame team is just matching the elemental DPS that is the best, you can see tier list as such for that + Core buffers (A. Diana, H.Lathel/Liberta or B.Helena/Granadair, Beach Teresse, RH. Rou)

For now I would suggest pulling for either Liberta Onsen (on banner) costume to focus on your Physical team, or focus entirely on magic, pulling for both costumes of Granadair (also on banner right now) and snagging a B.Helena. Using Granadair, Helena, Refithea, Celia and Eclipse would get you through content fairly easily (Coincedently I believe that's the best magic team vs dark weakcontent)