You demonstrate how much you know about warhammer when you call Order "alliance". Luckily Order isn't a fluffy band of banal boy scouts like alliance is.
Anyway, I've been testing the two classes fairly intensively (having wanted to play the KOTBS since it was announced long ago). While the KOTBS is relatively similar to the Chosen (which isn't a bad thing at all, given how much an aura tank, and human at that, is needed and wanted on the order side), the black guard has a definately different gameplay compared to the Iron Breaker. They both are definately enjoyable experiences to play and add a lot to the variety and choices that Warhammer Online offers in term of classes to both sides.

The fact that they have been added so fast simply demonstrate that Mythic is working hard and efficently to make a better game on all levels.