Performance Tuning :: Maximum Wait Events On PX Deq - Execute Reply?

I have a partitioned table with degree for parallelism defined as 10.

I am getting maximum wait events on PX Deq: Execute Reply.For 2 hours trace the wait event is almost 1.5 hour.

I have done some seraching and i found this.

Quote:
In principle:A parallel query against a partitioned table will use one slave per partition if the query is thought to span multiple partitions, and it can use all slaves on a single partition if the query is thought to target just one partition. Unfortunately, this is NOT strictly true.

It is possible for the optimizer to decide to use parallelism at degree M when accessing N partitions. Sometimes this can lead to very inefficient, brute-force, processing when a more efficient path is available. This can be a particular problem with multi-table joins that should be partition-wise joins. You may be better off leaving the tables defined as non-parallel and adding explicit parallel hints to the code for critical queries.

So i have following questions
1) What is the meaning of PX Deq: Execute Reply.
2) Is this not recommended to use DEGREE clause in Partitioning.
3) Defining DEGREE clause in partioning of table will automatically executes DML on table PARALLELY same a PARALLEL hint clause