There is a helluva lot more behind this than just importers taking too long to clear.
The port infrastructure cannot handle the amount coming into Qatar, the customs formalities do not often allow for an expedited clearance, etc.
As for most if not all going through Jebel Ali (as commented by a ready), this is not the case... many importers are, indeed, diverting to Jebel Ali because of exactly the reasons above. Plus, it increases their costs considerably now as they need to truck to Doha. the port can still not handle the amount coming in.
Look at south africa.... the country allows for pre-clearance before goods arrive - this expedites the process tremendously and exams (which are currently on virtually every container that comes in) are on a random flag system.
Even with the pre-clearace, you have 3 free days.... after that... it is approx $150.00 USD per container per day.
This implemented years ago and you can bet importers were moving their butts to get things cleared.
If anything in the short term (since no infrastructural improvements will happen fully for the next 10 years), they need to improve the customs formalities - what worked 5 years ago isn't working now with the volume - and then implement a financial impediment to containers being held.
Plus, they'll see a revenue boost from this from the containers hitting Doha port again.
Just my two cents.

Brin