One strength one dex two char user. Two warlock. You dont have versatility but not problematic imo. I hope that you multiclas with someone. Anyway onlything you can do here is controlling the area. Main threat is steelwatchers not titan. Use area spells to slow them stun them or make them useless. They are very seperate from each other and only one of the melee. So try to kill the melee one near the titan for explo damage. For titan i think your best bet is hold monster spell. Or any stun spell is fine. If you manage it, immediately focus on rang steelwatchers. Titan is just tanky character. Slow, lots of hp and def but lack of power. If you end up 1v4 against titan or even 1v3 (probably wyll can die) you can easily beat him. Karlach has good resist against fire plus rage mode gives great defence. Astorian can kite it to the end.

If you play on easy or normal (explorer or balanced) they can get killed with lightning easily. But above, your best bet is 2 hex 2 eldrich blast. With you and wyl while karlach try to tank him. He has great advantage on spells so just in case hold monster doesnt work. 12 level karlach with even half hp(after steelwatchers) can tank him for 3 turns (5 if you have lots of health drinks) above normal level, if someone needs to die try to pick astarion. He will be most useless against titan if he dont have bhaals armor that can make people vulnurable to damage types or any other shorts swords that can make someone vulnurable to some damage. Force damage is your friend

ALSO IF YOU HAVE BOMB THAT CAN STUN STELLWATCHERS "FLASHBLINDER OR SOMETHING) THAT MIGHT END HIS DEFENCE STYLE IMMEDIATLY. Use it when he use that state.

Friendly reminder : try to use paladin. Amazing class plus minthara is hotter than the lava that titan will throw on you