More demanding,visually, and badly coded are fairly different reasons for hardware to perform the way it does.
While i havent played ESO i have played Guild Wars 2 a lot and i can say it performs badly because it's an MMORPG that cant handle the "Massive" part real well.
If you're off in a map alone or in small groups,it runs great.
That's due to the engine being a rehash of the same engine they used in Guild Wars 1 which had vastly smaller amounts of people on the screen at any given time.
Will ESO have more demanding visuals? Its probable since the game is much newer. Will it perform better than Gw2 in its most demanding moments? I hope so.