It is good to know poplar itself isn't to blame. It appears to have some very good qualities. I was able to get a few to straighten with a friction rub using a piece of leather. If that didn't work I was going to try heating them up with a heat source.
If I have to purchase over spined shafts I may as well just buy 100 3/8 poplar dowels for the same price. I was just trying to save a little work and get something already spined and sized correctly. The funny thing about this is they are sold as higher quality shaft and are "matched". I bought some dowels local last week to make traditional arrows with and had them made up and tested in less time than it took me to get these shafts to a point they would roll on the table. Out of 12 shafts 9 where bent so bad the where a goo 1/2" off the table in the middle or one end. The wood was so dry I'm sure that is why I broke the first two. I thought about soaking them in water and then rolling them. It looks like most of the benns are right at grain runout points which is scary.
I won't return them because this is a learning experiance for me. I've always used cedar in the past and it is just so easy to work with. I won't complain about the vendor until I have more information to draw from. If I order a 100 dowels and don't have these problems then I may bitch up a storm.
I really wanted to share this just to get a feal for whether or not this is normal for this type of wood shaft. Heck I've managed to get 12 shooters every time I've ordered cedars from this vendor. The last batch was a little "iffy" but they all made arrows.