As a Veteran German player, my advice to you is, do not get the card that allows you to train settler wagons just use the cards to get all your settler wagons. Pretty much with Germany what you want to be doing is using your cards to get villagers and build your own army. The card Artisans is worth it though.
The main reason for not getting the Settler Wagon train card is...
1) Train times are extremely slow.
2) far to costly, 100 food and 100 wood.
3) The enemy focuses on these with their horse raids, so you have to keep them by the towncenter.
They are good for distracting your enemies troops though