Oops, wrong faction. I meant Vasari Loyalist, the one with the huge teleporting sting ray. And as far as fleets go, mine appeared to outnumber them at the beginning, at the end... not so much. 

I see a general lack of flak in your fleet.  Flak do well against LRF.  Also, if they're bringing in that many high level capitals, spam bombers.  Critical mass bombers > all.  If they have a Halcyon, knock that out first.

Also, you don't need that many Kortuls.  Kortuls are good because of Jam Weapons and Disruptive Strikes (though for reasons I don't understand, they think the weapon cooldown on Power Surge is a huge boon to their fleet's damage output).  It doesn't sound like they had that many SC and you probably didn't need that much AM drain, though against Advent, you'll want some.  You should have had more Skirantras.  Repair Cloud is a spectacular heal ability, not only does it heal hull quite well, but it also heals your SC, helping you maintain air supremacy.

On top of everything else, unless your titan has unlocked The Maw, you shouldn't be having it in heavy combat as it frankly sucks at it.  Also, since you are playing as VL, you can always strip a few worlds near the border so the enemy has to phase jump repeatedly to get to you, draining their AM in the process.

Since you were defending, you should have had a culture bonus.  Unless they have the culture bonus, the Advent are very weak to phase missiles, so Assailants and Bombers are your best friends.  Subverters are also very good for taking down enemy frigates, though it sounds like at this point you're more into the late-game capital battles, so use fewer LRF/corvettes and more Bombers/Overseers/Enforcers.

Enforcers for the VL become downright devastating because wave cannons can be upgraded to +70% damage, making them the most powerful frigate in the game as far as straight DPS goes.  In capital fights, you'll also want both levels of Reintegration for your Enforcers because they'll be under a lot of pressure from incoming DPS from Chastic Burst and the like.

Spread your fleet out as much as possible so that Chastic Burst+Malice doesn't nuke everything.

The Eradica is weakest from it's sides.  Flanking it will reduce the DPS it can deal to your fleet.

Throw your Orky straight into the heart of the enemy fleet (make sure it has both levels of Debris Vortex).  This will allow all 16 bank targets of the Orky to fire.  When maxed, that's about 2000 DPS pouring into the enemy fleet and about a third of that is Phase Missiles which as mentioned before is great against Advent ships.

OK I can Attest to the power of nano leech. I'm and advent player and i had a fleet comprising of 2 radiance, 2 progenitor's, one halcyon, and one rapture and a  eradica at level 6 with 43 illuminators 20 disciples and 15 defence frigates and 10 guardian's. I destroyed its fleet with ease but nano leech kept it alive with repair rate exceeding 1000 per sec at the max. I killed it but it took 45 min at least. My caps survived my frigates and cruisers not so much and only my rapture being destroyed and my one Radiance taking heavy damage. I almost forgot all cap shipswere above lvl 6, 4 were lvl 9 and 10. Op does not describe that titan its just plain wrong.