Actually I think scenery has a very big impact on DTV. In my opinion, DTV maps should be:
1-Equally balanced. So it won't feel like a waste of time to play harder maps, while there are easy mode maps.
2-Should be fun to play. the maps has the most impact on the gameplay. The maps that has no use for archers, are boring for archers for example.
3-Should consider the behaviour of bots. One of the waves have riders who use nothing but great lances, which is plain useless because there's no space enough for them to do a couched lance strike.
4-Shouldn't be too hard or too easy. Blank 8 map is too easy and Arena map is absurdly hard. Find a good balance for them.