wowcoop

The main role of a destroyer, as far as battle is concerned, is destroy battleships.  Yes, spotting and capturing/contesting is also a part of your job but fighting is a large part of that.

In order for a destroyer to kill a battleship easily he must have no distractions i.e. other ships.  You should not be engaging in battle with other destroyers or cruisers.

It is the cruisers main job to kill destroyers so that you can do your job.
It is the battleships main job to kill cruisers so that you can do your job.

Pinpoint targets for your team so that they can concentrate fire on them.  Obviously it doesn't always work out this way, say you have no cruisers, or their are too many destroyers to avoid, but generally this is the way it should work.

Once your clear of distractions it should be much easier to finish your main objective.