I've watched baseball for maybe 20 years now. Since then, the game has changed, and has changed again since.
- Steroids has caused an explosion of power hitters. I remember watching some old games of Reggie Jackson. If he played today, he'd have the build of some of the lead-off hitters of the steroid era, much less a middle of the lineup basher. Cleaning up the game is starting to see a return to normality.
- Teams have become more comfortable with sabermetrics. As such, bunts and stolen bases are quickly becoming extinct.
- Perfect games/No Hitters are becoming more frequent.
- Pitchers were ruining their careers playing in Colorado. Humidors seems to have reversed that unfortunate trend.
- Relievers are being used more and more frequently, a trend that's not likely to ever change.
- On the horizon, instant replay is soon to be implemented.
The point being, in 20 or so years of real life baseball has shown a lot of evolution. My fictional league has been in existence for about 40 years, thus you would expect twice as many changes. Some people have run their leagues for over 100 years. I don't necessarily mind "deviations" such as catchers being traded mid-season more frequently. Things change, things evolve.
What is normal? "Normal" is relative to the needs of the league at that moment. If the game doesn't have a lot of decent catchers at the moment, then you may very well see a lot of trading. Even if you use the MLB quickstart, the financials aren't quite a duplicate of the real world, and maybe finances are contributing to this particular evolution. Who is to say that this isn't exactly what would happen in the real world if the league's composition was the same?
So I am hesitant about labeling this as a problem without more information.