Not particularly a balance issue, but sure a User Experience issue.
When group moving Water units i shouldn't be forced to use shift+g to break formation, in order to get them moving all at once. it's annoying that especially those in the back row of units start moving way later than the other units, while beeing massacred by a pushing force. This probably has to do with formations.
Another issue, probably related to this problem, but a separate annoyance, is that ships have a veeeery wide formation. Formations usually exist to make it possible for all units in a row to fire at once when an enemy appears in range, but with a very wide formation many short ranged ships like frigates and t1 subs are way out of position (far to the sides) when enemies appear. With a more dense formation this wouldn't be happening.
I do see why it can be hard to fix it, because of clumsy pathing this game has, but i hope some tweaking can happen.