I dunno, it seems to me advent is perfectly capable of dealing with TEC loyalists, Titan abilities included, although I have to concede that in the recent instance my titan was higher level (just one or two levels). Infact, it seems advent really rape TEC, from what I can tell: they are a Homeworld swarmer's dream come true.

I was Advent Rebel fighting against an Unfair AI's TLT in this situation :-

*I owned the gravity well, had culture, full research (all trees)

*Had a full compliment of tactical modules built up (a bunch of synergied beam arrays, a bunch of hanger defenses, a phase inhibitor and like 3 repair platforms all bunched together near a starbase for sharing the Synergy shield buff all around)

*Maxed starbase "out in front" (closest thing to the enemy ships) with 3 x Preservation and 2 x weapons, the rest of the upgrades I bought were non-combat (trade and culture I think)

*I had a total of like 12 fighter squadrons from the hangar defenses, and allocated them all to fighters because I anticipated an enemy attack with a swarm of their own bombers and didn't want them to take down my Starbase

*About a minute after the enemy fleet hits the gravity well, my own fleet arrives: 2 level 8 Progenitor capships and an level 5 advent rebel titan. I already have my Radiance flagship in the gravity well, but it's hanging back just behind the starbase and the beam arrays so that only the LRMs can attempt to hit it (and it seems they're more interested in hitting the beam arrays anyway).

*I take a look at the enemy fleet and they have a level 4 TLT, 2 Ogrovs, several LRMs,  Level 5 and 6 Kols, a level 8 Akkan, 2 level 4 Sovas, a level 6 Dunov, and a total of about 12 assorted frigates/cruisers (percherons, kodiaks and hoshikos).

*The AI rushes my starbase head-on with the softer ships, and the maxed weapons obliterate all but the cap ships and titan in a very short time. This is about when my titan and backup fleet (the 2 Progenitors) arrives. Their titan is still at like 95% shields because it's sitting out of range of the starbase, hammering away at a hangar defense I have sitting out vulnerable on the side of my primary defensive line.

*I go after the TLT with my titan (which is 1 level higher than theirs) and my 2 Progenitors. Later I cautiously throw in the flagship for extra DPS.

*A lot of fighting happens. The end result: I lost a bunch of my weaker modules (beam arrays and mineral extractors, mainly) and my capships had about 50% hull each, but their shields were doing well because I was able to retreat them mid-battle and use the shield restoration ability. The enemy titan fought to the bitter end but was destroyed. It seemed very interested in attacking my flagship and my modules, so my own titan was hardly damaged. I ended up destroying all of the capships, too, because they couldn't retreat; my phase inhibitor was cleverly placed, surrounded by a ring of beam arrays, repair platforms, and the starbase on one side -- so the enemy would've had to target it with their entire fleet from the very beginning in order to destroy it, but since it's the AI, it didn't do that.

*Considering the odds, and considering how heavily I inflicted losses on the enemy while only losing a few modules and taking a lot of hull off of my capships, I think I did pretty well... I was feeling the annoyance of the TLT ability for sure, but I used the gravity well advantage plus things like repair platforms and the starbase's superior firepower to eventually wear down and destroy the titan. Basically it tried very hard to punch through my defenses, but I had so much pushback built up that it wasn't able to break through. And it couldn't repel the damage being dealt by my starbase indefinitely, because even against a titan that thing can DEAL. I used my flagship to lure the titan into range of all three of my starbases's weapons, and it didn't last very long after that (especially while being targeted full blast by my own titan).

I also used the mobility of my reinforcing fleet to my advantage: I killed their Ogrovs right at the very beginning of the battle, because I knew my titan and capships could withstand a little heat in order to destroy the Ogrovs before retreating back within range of my modules, which then provided a lot of much-needed soaking up damage from the capships and titan.

You're right, the Advent need a unit that is able to deal good damage to the TLT, without having to rely heavily on abilities.

Maybe the Destra Crusader? It's the closest thing the Advent have to the Kodiak. And I've seen Kodiak spam in the dozens or hundreds prove frighteningly effective against almost any ship. Yeah, you'll probably lose a TON of Crusaders, but, you beeline for the enemy capships (you did say the Marzas AoE are going to do more damage than the titan, right?), pop 'em before they can take out your crusaders, then target the titan.

Sounds far-fetched, especially if they destroy all your kodies before you can pop all their marzas, but I wouldn't discount it as a viable strategy. If you deny the enemy the opportunity to use those AoE synergies you talked about, you might have a chance to beat a TLT (your chances are greatly improved by bringing along your own titan and a few capships, of course).

Then again, I'm unsure when you'd ever have a titan vs. titan battle in a neutral gravity well. This seems like an improbable event, so it doesn't make sense to me to postulate what might happen in this situation. I'm sure it might come up if you own a planet on one side of a space junk and the enemy owns a planet on the other side of it, but even then you can build a starbase in the neutral sector.

In fact, thinking about this some more, it seems like an advent starbase, fully upgraded, is a most excellent way to either scare off or destroy an enemy titan. It puts out more damage than almost anything, and it doesn't give a rat's ass whether the enemy is disabling its abilities or not, as long as it can shoot. And titans aren't particularly optimized to destroy starbases the way that anti-module ships are, so it's still going to take the titan some huffing and puffing to down a starbase. I can't see a TLT being able to take down an advent starbase and a similarly-leveled advent titan (loyalist or rebel), unless the TLT had a superior amount of fleet support behind it. And if it does have a superior fleet, gee, it probably deserves to win.

So, moral of the story? Use advent starbase spam like there's no tomorrow, and be sure to stick your titan right where the enemy TLT is, so that you pretty much force an engagement between their titan and yours plus the starbase -- if it's an AI, you'll probably get the desired engagement and win; if it's a player, they'll probably run away and you "win" by default.