Some lint will always get by the lint screen on ANY dryer. None of these screens are perfect and, YES, this is normal. This is why a routine inspection of the dryer exhaust ducting and internal cabinet are recommended about once per season to ensure the dryer remains running efficiently.
However, there are some things to consider when it comes to dryer ducting installation. The following link explains:
Most excessive lint problems are a result of improperly installed dryer exhaust vent ducting. An excessively long run causes more resistance on the blower motor which will reduce its ability to sufficiently push all the lint out of the exhaust. Each bend in the run also creates choke points where lint can potentially accumulate.
The following link can give you some additional pointers on dryer heating efficiency:
You may or may not be experiencing poor efficiency, but if you are getting excessive lint build up, it will eventually lead to longer dry times and a dryer that will actually overheat to the point of failure. Excessive lint build up is also a fire hazard.
You will experience this problem with ANY dryer as the performance of the best dryer will alway depend upon how well it is installed. This is not to imply that you have done a poor job in installing your appliance. I'm providing this information to give you some things to consider. Most consumers are not aware of the fact that they still need to perform routine maintenance on their appliances to make sure they run efficiently and problem free.
If you have any questions, please post back and let me know, I hope this information is helpful to you.