Tbh, the only champions who purchases Ravenous Hydra is mainly Fiora
is a rare case, while the rest just prefers
to be its sub.
I mean is there any chances that the power distributed to both items be able to made as similar & fair as possible? Such as lowering down Titanic's base AD more & scale it a bit more better with HP?

True, the number of champs that build it is small, but those who gain significant power with it. And if there's an item you want to complain about its existence, pick on Ohmwrecker. How many champs build this item again?