If the land tax is greater than what you can make renting, then that means your land is improperly priced. You can prove it by putting it on the market and no investor will buy it at that price because they would lose money and thus it would have to fall until the land tax is less than what they can make from rent.

Now, if you abolish zoning or rezone places in addition to a land value tax, it could work as the investor could build more housing for the same land thus splitting the cost over multiple renters which I'm sure is the intended affect but a land value tax won't work without changing zoning laws and at the end of the day, it's all passed onto renters.