Question on mixing when using Dim Pro and Session Drummer

Yes theoretically but they may still require more.  

The beauty of your question is that there's really no wrong answer.

No doubt you audition various sounds for you DimPro bass and Session Drummer kit.

Once those sounds become part if a mix if other sounds as you've mentioned they might benefit from some more processing.

Play around with it and listen and learn.
Can I recommend you get yourself a copy of the free iZotope Mixing and Mastering Guide. I don't have a link as I'm using my phone at the moment but just google it. It's regarded as an industry standard primer for what you need to be learning at this time. All the best.

Mike's answer is astute.  If you look at my answer its noncommittal.  Your question is so general it requires a general answer.

It also depends on what is meant by processing. One could make a case for any adjustment made to the mix as being processing. That would include volume balancing, pan and so on.

Blue Note made recordings of jazz with two mics going to a stereo tape recorder with not much processing if any. No mixing was done at all. Yet their recording are some of the best ever made of jazz. The mix was made by the room and the mic placement.

We now have an enormous control over what we produce from our DAWs. We also tend to have a lot of plugins that because we have them we want to use them.

With ITB production the samples have already gone through a great deal of processing. Plus all sample players have an amazing amount of their own processing and control built in.

It seems to me that one can spend an awful lot of time tweaking a sound to the point it is nothing like what it was recorded as. I think it all depends on what you want. Where you are going with what you started with.

It can be looked at as a series of decisions made from start to finish. 

Also there is the world of sound creation.  If one only records real instruments than that part of DAW use may not be used. However there is nothing stopping one from doing that.

Really you have asked a question that is one that is only answered with adopting a sonic philosophy.  Even then it will be a matter of your own experience and knowledge.