Would the banning of Tendrils force people to play different, more interesting combo decks that require a more complicated series of card interactions? Maybe.

Is it necessary to ban Tendrils to ensure the health of the format? Probably not. As many people in here have already noted, Tendrils combos make up such a small portion of the Legacy metagame that making that particular strategy unviable would do little to change the format as a whole.