BT over Mel any day. He is just so much more versatile since he tanks but also buffs damage. I have both Colen and BT maxed and Colen is never leaving the bench. I bring BT over Colen against titan since he adds survivability and the extra damage is more valuable than what slow Colen does to a single target.
With tib lowering defence and bold buffing damage you have a good combo.
the green one is difficult since I don’t like slow heroes much. I see you also have skittles. I haven’t played with skittles or LJ. In the end I would chose LJ. His special has similarities to Li which is the top 4star defensive hero imo.
Also: don’t eat Brianne. Try leveling her and try her out against titans. As long as the titans you are facing doesn’t one shot her, her special stacks with bold and banners and can be a nice boost instead of bringing LJ/Skitles/Mel to a titan game.
Lastly: don’t afraid to bring several heroes of the same colour to a titan game when to colours match the sensitivity of the titan.