Titans have various level of cunning. Stuborn is the most common level. Thoses single-minded titans will go straight from theirs spawns points to your base. They *will* attack anything in theirs paths but will not otherwise deviate from their objectives.

Decoy will have a limited effect on them : they will choose a random target between the constructed decoys and your base.

They will go to their target by the faster path, following routes and avoiding tangleweb as needed. They may quit their route if suffisantly intimidating turrets are threatening theirs paths.

The best way to kill them is to put some turret with a good views on their path. If for some reason they flee your turret, you can either try to cut every access, forcing them to go path at least some of your turret, or use Scarecrow to block theirs alternate path.