It is possible to create very nice animations inside of Daz, it just takes a bit of care and patience. The Daz tools aren't superb, but they aren't
complete crap either.
is the some plugin or something that can facilitate the animation process?
Not that I'm aware of. That being said, mCasual publishes some scripts that help. His "AutoLimb2015" helps fix hands and feet in place. (The new versions of Daz have Inverse Kinematics for this, but I find that tricky to use.) He also has a "KeepOrient" script which, in combination with AutoLimb2015, does a reasonable job of having a characters hand or foot "stick" in position to a table or a wall or whatever.
is there any other software that can be used to animate and after bringing the animation back to daz?
You can take Daz characters out to other pieces of software. I've been told that you can do pretty decent animations with Maya or 3DS Max or MotionBuilder and then bring them back into Daz, but those packages are VERY expensive. You can take a Daz character over to Blender, but if you use Daz's new converters, you can't (easily) bring the animations back. If you don't use the converters, you haven't really gained anything, because all you have is the same FK skeleton that you have inside Daz Studio. I've been fiddling with iClone - again, you can get Daz characters in, but again getting the animations back out is a challenge. The big issue with many of the "external" programs is that they don't "understand" how the split bones in the arms and legs work, which means they try to apply twist to bones that Daz doesn't allow to twist. (I've been trying to program a solution to that.)
Bottom line - I strongly suspect most of the animations you've seen
were made in Daz Studio, they were just made with a lot of care. (Of course, it's possible that some of those animators have developed their own custom mCasual-like scripts or whatever to help them along...)
