Board Thread:Fleet's Prepared-ness/@comment-28828142-20180212191757/@comment-24930367-20180213232131

3-2 works great for leveling multiple DDs, albeit might lead to less EXP (never bothered about counting EXP/hour, that's for nerds).

CV flagship - 3DDs - a submarine - BB (normal works, but aviation works better).

As you can see this depends on rotations, but in exchange the EXP will be split rather equally.

If I were you I'd push for Class B difficulty at first with Lv. 40 ships, only if the rewards outweighs the cost (95% of the time it isn't) and you have everything you need in that particular map. But this also means you need to plan ahead which is going to where, which isn't fun.