Suggested Strategy Edit
This ship is all about 3 things:
Mobility: You are fast, especially with the upgrades to speed and a 5 or 10% boiler. Use it. Kite as much as possible.
AA: You have 7 double cannons per side to rain hell on enemy planes, learn to use them to take down the enemies eyes and everyone on your team will love you, trust me.
Gradual: This ship, unless getting approached close up by a sub or a DD is all about gradual ( or sequential ) firing and since you're supposed to be kiting, you won't use salvos often. I couldn't really have a lot of success with the Atlanta until I switched to gradual. Use gradual, keep your distance, try to stay out of sight and harass them until they sink. At first they won't pay much attention to you because you don't do a lot of damage per shell, but pretty soon they'll realise their error and when it happens, most often than not, it'll be too late. I racked 200k+ damages and multiple kills even on big targets in countless games doing this.
Torpedos are a last resort in case you got target focus and suddenly you notice that you've sailed right by a big bad CA or BB, keep them on contact, narrow and fast unless you need to deal with a sub, then you can change to proximity and wide. On rare occasions you can use them to harass enemies at long range or try to keep them at bay by using slow and contact or proximity ( depending on your target, prox for DDs, contact for everything else ) and wide. Of course they can always be usefull against a CV here and there too, but most of the Atlanta's damage comes from its 8 guns, 7 per side and 5 aft ( perfect for kiting ). Most of my big points games never involved any torpedos. I repeat, they're a last resort "oops" weapon unless you must hunt a sub.
Which brings us to the next topic, escort.
This ship is one of the best, if not the best escort ship in the game for the bigger guns, it can almost do it all. Shoot down planes, ping that sonar for a sub you know is around and would like nothing better than to hit a volley of torpedos on that big juicy BB you're escorting, make sure that the other team DDs stay away from the BB while he shoots at the bigger targets ( and you too if you have nothing better to do atm ). Sometimes go to one side or another to give the ship you're escorting a little vision advantage. And finally it can dish out a LOT of damage. I can't recall how many times an enemy BB or CA underestimated me and didn't notice until it was too late that my gradual fire was chipping away at its DP, not so slowly, until he went boom.
Be carefull tho, when the other team sees that you're a threat they'll send planes after planes and DDs will try to spot you for the enemies big guns or the big guns themselves might even manage to maneuver themselves into their vision range to tear you up. Always be on the lookout for this, if it happens, use your speed, not your guns ( tho if you can, keep laying fire until the last minute, its what those 5 aft turrets are for ), avoid islands at all costs and look at the map, you might be falling into a trap, right into a pincer maneuver. If you get chased you can use it to your advantage and turn the situation around if you can run and lure him/them right into the arms of your teammates, I did this numerous times and its always fun once they're engaged by multiple ships to suddenly turn around and tear it/them up.
That's it for now, if anything else comes up, I'll update it.