Okay, I'm going to do my best to break this level down for people. Hope this helps.
Pregame:
This is a Lightning Recommended level, so badges that limit damage taken are helpful here. The last third of my attempts were all perfect except damage taken, usually over by just a small amount. I believe you need to be below 5,000. If you have the "moderate" level for reducing damage on Lightning recommended levels, you should be more than good to go.
Second Badge that bears mentioning is the Stamina Fruit badge, or the one that speeds up reduction of the Weak Point gauge. If you have it high enough, a single hit will be enough to break the gauge of Fiery Aeralfos. THIS IS KEY.
Obviously anything else that makes you stronger helps. When I completed this map for my A Rank, it was in about 12-13 minutes (need below 15 minutes) and with about 1,400 kills (I believe you need at least 1,200). My weapon was the Wind Waker with a base power of only about 120, and only the +Lightning skill. Zelda's level was about 45-46 (if you've been failing this map a lot, level should not be an issue).
Step 1: Enemy Captain- Aeralfos
The moment the level begins, run forward and slightly right. There is an Outpost Captain for the Rogue Faction here. Kill him to supply some more troops to this area. Turn left, and intercept the column of approaching enemies. At their head should be a Fiery Aeralfos (FA). Kill some of the minions that aren't directly adjecant to him, and wait for the mission prompt to tell you to attack a key captain. This is important because for the most part, FA won't start attacking with his flame breath until this happens. Don't attack him directly, as he will just guard and waste your precious time. Instead circle at a slight distance and wait for him to fly into the air and use his flame breath. As he does this, position yourself so that when he lands and you attack him, there will be many enemies behind him. The moment his gauge comes up, strike! Hopefully you will break his gauge in one hit, and your WP Smash will hurt not only him but kill the mobs behind him. This will rack up your kills and charge your special gauge. You can also get in a few opportunistic attacks on him, but he's liable to block a combo of three or higher. Repeat this about 3 times, that should be enough to bring him close to death with some change left over. Once he is dead, we're on to step 2.
Step 2: Messengers!
When you are prompted to take out the messengers, immediately book it up along the west side of the map, through all the Rogue forces here (Yellow). It's tempting, but don't get bogged down in any of the fighting here. This area is completely unimportant. Instead, make for the keep that is immediately west and north (Up and left) of the allied base. You should intercept the first messenger here, a Gibdo. Kill him and take out as many enemies as you can. Take the keep as well, though this is liable to happen on it's own as collateral damage from your fight. Now, here's the kicker. That second Messenger? Check his position on the map. 9 times out of 10, when i played this map, that messenger would get stuck on a corner and go nowhere! If he hasn't yet jumped down and is still somewhere up on the stone walkways, you're golden! And if he does come down, chances are you'll intercept him in the same area as the first. But do not go hunting him, because HOLY CRAP STEP 3!
STEP THREE OMG ALLIED BASE!
Chances are that Volga, two Shield Moblins (SM), and sometimes Wizzro are ravaging your base! At this rate it won't last long. Once you've killed the Gibdo messenger, head straight here! You will either intercept them just outside the base, or they will already be inside. The SMs are horribly weak to the Baton, and a single Special attack is enough to kill them utterly at higher levels. Kill all the Captains here, and as many mobs as possible. I found that the w-w-s combo (bars and notes of electricity) are excellent at this. Volga is a big sticking point for some, he can hurt you quite a bit. Here are some general tips.
The Wind Waker has a longer reach than the "behind the back" camera lets on. Learn it, use it.
The w-s combo is great for juggling.
Use the surrounding mobs to quickly fill your special attack gauge, or failing that, use the jars located in the base.
Blessing In Disguise- Volga's Dragon Form attack: This is actually one of his easiest attacks to dodge and counter. Keep running in wide circles around him until he blasts the fireball, and steer clear of it. Then, as he comes piledriving into the ground, the trick is the rapidly swirling sounds he makes. Use that sound to time your dodge just right, and end up right next to him. This attack leaves him open for longer than almost any attack he's got, but it's still a small window. Punish him.
Lastly, it should be mentioned that if you don't help the Goron Captains battling Wizzro, then he's likely to be in your base too by now. Dodging both of them while not taking damage is very difficult, so of all the allies to ignore, the ones fighting Wizzro are not one of them. If Wizzo is still elsewhere, use the Magic Gauge jar that Volga drops against him. This is to take Wizzro out quickly, as he has the highest DPS of any unit you'll face. YOU DO NOT WANT A PROLONGED ENGAGEMENT WITH WIZZRO.
Step 4: Return of the Fiery Aeralfos' Revenge of the Return.
Killing Wizzro and Volga will prompt the Feirey Aeralfos who commands the Rogue Forces to advance along with two Gibdo Captains. This is good, because it saves you needless traversal time. You'll likely meet him in the keep where you killed the Gibdo Messenger(s). If everything is going smoothly by now you should have in the neighborhood of 800 kills. Don't worry, you'll rack more up quickly. As before, mainly rely on smash gauge attacks to hurt the Aeralfos and Gibdos, and try to catch other enemies behind them. However, the Gibdos are much more vulnerable to normal attacks and combos so don't waste your time waiting for them, even though they spam their shout and reveal their gauges readily. As long as you can finish things off here around the 11 minute mark, you should be good. But be warned! Usually during this conflict your base will be endangered at least once, possibly twice. Pay attention to the 'Girahim's Forces are advancing!" prompts, and kill them in your base or near it. They should only be Shield Moblins, which as stated before are utterly doomed by the Baton's special attacks. After you kill FA, you should be nearly done.
Step 5: Kill That Fool.
Head up the steps towards Girahim's base, and go left (towards the keep that the other Gibdo Messenger is likely still stuck near). If you're in need of kills, quickly take this keep, but pay attention to the magic jar near it's eastern exit. This will hopefully contain a "Full Magic" jar. There will be plenty of killing to be done in Girahim's base too, so if you're at least at 1,000 or 1,100 going into it you should be good to go. With luck you'll be going into your fight with Girahim with full special gauges and magic. Wait for him to do his cutscene (or turn mid-battle scenes off in the settings menu as of the new update), and spam your specials on him all you like. Once they're done, trigger your magic gauge and keep pummeling him. This will break his guards, do more damage, and recharge your special attacks. Be sure to hit him with the triggered version of your Focus Spirit attack just as it's about to deplete. It has a narrow focus so don't miss. This will force his weak point gauge to show. Mop him up as best you can with more specials (if you don't have enough you can charge it up with mob kills or nearby jars) and avoid damage as best you can. Done right he'll barely even get an attack in edgewise with all your special attacks going off on him.
There, I hope this helps. If anyone needs any parts clarified, just ask.