I recently had a few endeavors in the world of fitting shafts. The first involved irons. I was out and about looking at new sets of irons to possibly replace my current eye 2's, and found monstrous differences in consistency between shafts. The DG S300 had terrible consistency, and I lost an average of 10 yards from my current set. However, the KBS Tour Stiff and Project X 5.5/6.0 worked great for me, tightening my dispersion to a ~20 yard circle (including mishits) with a 6 iron. Without mishits, this was further narrowed to between 10 and 15 yards. My second experience came with my 3-wood. It previously had a stock Ping TFC regular shaft in it. I knew this was too soft, as I am between a stiff and a regular Pro Launch Red, and Ping stock shafts are generally play 1 softer than they specify. I avoided my 3 wood at all costs, taking baby swings if I needed to hit it, and just using my 18* hybrid instead most of the time. Now that I have had it reshafted, I can finally hit it with confidence without duck-hooking it into the weeds or feeling like I'm about to slice it to hit a straight shot. This just goes to show that you need to AT LEAST get fitted for the correct stiffness, and you should definitely go out and try out different shafts to see what works best for you and your swing to get the most out of your game.
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This just depends on how far that person wants to take their game. Generally, players that take the game a little more seriously and are avid golfers will get fitted. Players who play once a week or less will probably not need to get fitted, or want to.
Last year was my first year of "serious" golfing where I played twice a week and sometimes 3 times a week. I used a very cheap set of Callaway X-20 clones with graphite shafts. They were +2 length and not fitted for me and were made by a local resident "pro". I picked them up (3-PW+Driver) for $100.00 so I couldn't pass it up. This year I revamped my set and went through fittings and the whole 9 and have become a single handicap golfer.
Fittings will be determined by the level of dedication you have for the game, I believe.
I had the problem with my shots all ballooning when I used the S300. Couldn't hit a punch shot to save my life, and spin was off the charts. Maybe you should try a stiffer/different shaft?