Myrmidons also don’t benefit from proficiency bonus to attack rolls with their weapons, because Moon Druid doesn’t have proficiency with those weapons.
Earth gets tavern brawler and with that the most dmg / attack /ac/ hp. But you are right from 4 myrmidons only 2 are useful water and earth. And from all wildshape is only 2 is good. For rare case panther is goot to escape.
I wish all of them would be lvl up scale up.
For example Beast Master animal companions are stronger then Moon druid wildshape.