One thing I thought WoW did well was every zone looked like a brand new place, it had more then 5 terrain types and many weird exotic looking ones. I fear Tamriel does not have many terrain types, there are 9 continents so I assume there will be 9 terrain types that will look very different from one another.

9 provinces in one continent called Tamriel (there are more continents on Nirn, but we won't visit them).

There's also a wide diversity of terrain within every province. Have you played single-player TES games? They show it very well. For example, Skyrim has cold, snowy areas in the north, plains of Whiterun Hold, forests of Falkreath, geysers between Riften and Windhelm. Morrowind has ashlands, but also fertile, lush Ascadian Isles and hilly Grazelands. Elsweyr has both deserts and tropical forests.
And the list goes on, so there's plenty of opportinity to create unique environments.

I don't think we will have any problem finding widely divergent environments in TESO. The full range of climates and flora/fauna of TES will be on display throughout the zones and we will be seeing many creatures and environments that have never been seen in the TES series. It will be glorious!

If you have played any of the previous TES games you know that environments can vary widely within the provinces. A player will have access to their faction's provinces, which will be comparable in size to provinces in TES games, so there should be plenty of variety. I'm really expecting and hoping ESO to have some of the most immersive environments in the MMORPG industry as this has always been a outstanding feature in TES games.