There is no such thing as delayed case. A case takes more processing time due to factors like more medicals tests or some information taking more time to be verified. Once the case is with IRCC, they just can't stop working on it.
Also, no two cases can be same, so there is no comparison to be done. For instance, some cases might not have any travel history, some cases have travel history to many countries, so validation take time, even though they have the same AOR.
Just have patience, if you do not have any complexity is your case, it will be approved. Due to Covid, processing is slow.