I haven't dived into the beta very much lately ( In the process of moving 
), and this is mostly based on my style of play, but shouldn't Titans be seen as a force multiplier rather than the force itself? The way I employed most capital ships in the old Sins was based on this, and it worked rather well. Much like the modern day tank, it would be extremely foolish to assault with tanks alone, they would be obliterated, but when supported by aircraft, light vehicles and infantry, it suddenly becomes an unstoppable advance. I suppose a better way to put it is when your various build of attack fleet meets the various defenses/defender fleet or equal strength, the presence of your Titan would swing the battle your way. It should not be able to win alone, a well rounded fleet should eat them for breakfast, but when supported by frigate screens, repair vessels, long-range support, fighter craft, etc, it would become much much harder to bring down. So in essence it could:
Be a buff unit. -> Hands out either faction specific/purchased/starting buffs to anyone it is grouped in a fleet with. Things like huge targeting buffs, and/or fields large amounts of faction specific repair buffs for a nice passive repair in battle, or over-projecting shields for tougher shields on the ships.
Be a tank. -> Soaks up tremendous amounts of damage with plenty of armor plating, at the cost of some weapon ports being covered in more armor plates 
Be a sniper. -> A one shot - one kill weapon with a very long reload time ( with a minimum range to counter ). Think the MAC Guns from Halo.
Be a carrier. -> A titan would not only be able to field a ridiculously huge fleet of strike craft and bombers, but manufacture them ( with no penalty for being in combat), or perhaps be provided with a very large amount of extremely high quality (more damage, health, evasive ) strike craft/bombers.
Be a transport. -> A fast, lightly armed and armored for maximum room, it can arrive in system and drop off a set amount of pre-built and stowed ships for a surprise raid. Being a transport would also say buff the trade income for a friendly system it is sitting in or something to that nature
I'm sure with those suggestions my idea comes across clearly.
Something else ( I have also posted in the Corvettes post ), I think any element of "Stealth" is non-existent in Sins. A "submarine" class, for lack of a better term could perhaps be filled by these corvette class. Small, agile, sneaky, you could have them sit in an enemy well and gather intel, perhaps even upgrade their intel gathering ability, such as if you are on the home planet you can see what they are currently researching. Perhaps conduct covert operations such as factor sabotage, or bringing the trade center offline for a short while, even leeching trade income. If the circumstances were correct, I.E culture ( not sure if culture still matters ), they could use propaganda to incite uprisings, causing planetary damage before the main fleet even arrives. Granted to do most of these things you would have to give them stealth, so counter stealth with a scout ship, or even if they move to close or while they are in FTL flight. I think Rebels could steal profits and incite rebellions where a Loyalist operation would be more professional in nature, taking a ship factory offline for a short amount of time, or slowing research.
I see a ton of potential for various factions, but alas, my battery is about to die on this poor thing, if more ideas are desired, I would be happy to share.
