If you're wondering how people are farming things so fast, the answer is that the team has been built and optimised well enough that they can throw them in battle, press auto (or auto skills) and do something else then come back and check them once every 2-3 minutes.

For raid battle it's more or less similar, you go in with your best team, press auto, leave burst on, and start whacking after your initial round of debuff. However there's just some thing you can't do as some of the bosses are downright OP and need your full attention.

As for levelling, you can put the hime you want to level on the sub team.