Pete, sorry I am late to the party on this one, just saw your post.
The Tusker 190's use the same blade as the 155's all the weight difference is in the ferrule using thicker steel to make the weight. As a result the ferrules on the 190's can be a bit oval. When you use heat and your hot melt it won't matter, the adapters will still spin true without much trouble when you mount them up.
As for the blackened tip, I have never seen one like that no that it not typical so I don't really know what's up with that.