R11driver

If your swing speed is indeed around 100, then you should be using a stiff flex shaft. The problem will be finding the "stiff flex" that works for you. Unfortunately there is no standard for shaft flex between manufacturers so a stiff Aldila can be different than a stiff Graffaloy, which can be different than a stiff UST. If you have a place that does club fitting, or a golf store that can put you on a launch monitor, that's the best way to go.

I just bought a set of the TM CB irons and really like them. I tried them side by side with the R11's and there was no comparison. The R11's were consistently shorter and harsher. To me, there was a big difference in the way they played and felt.

Launch monitors and computers are fine. Just make sure you get what works best for you. Don't let them push "numbers" like spin rate, launch angle, etc. There "are" norms, but get the clubs that give you the best distance/consistency/performance. As an example, I just bought a new set of irons. I had several in mind but wanted to try them out and see how they performed. I went to a local Golf Town store and got on their launch monitor. Tried several models including the Razor x tour, and Razor X tour forged. Diablo tour. Cleveland CG 16 tour, and Taylor Made tour preferred CB forged irons. It came down to a choice between the Cleveland CG16's and Taylor Made CB forged. I was getting equal distance and performance on the launch monitor between these two where the other clubs were an average 5 yards shorter EVEN THOUGH they had better "numbers". I ended up the the CB forged because they were on sale. I've used them a couple of times and they are AWESOME.

If you are building your own clubs, you can soft step the shaft when you tip trim. If a 4 iron shaft called for a 1 inch tip trim to play to a regular flex and you tip trimmed only a half inch, the shaft has been soft stepped. It will play about a half flex more flexible doing it that way.

To answer your question, it's not necessarily bad as long as the shaft make/flex is the same throughout the set. You wouldn't want a mix of stiff and regular. As someone else already responded though, if your new, it's better to go with a new set so that everything matches. Decent starter sets are fairly inexpensive. Steve