Here's an example of what powerful hitting mechanics look like, particularly with respect to generating power through the torso.
In this post I share some things we can do to correct the "shot put" type of arm swing you sometimes see in new volleyball players.
Here are some insights into how hitters need a good mentality and a full set of potential attacking solutions from coaching legend Julio Velasco.
Back row attacking - especially in the women's game - tends not to have a high success rate. If you do things right, though, you can improve that.
There's a lot of stuff out there about volleyball arm swing for hitting and serving. To put it bluntly, some of what you've seen and heard is plain bad.
A regular reader of the blog has an issue with hitters that can't attack with topspin. I've had that issue myself. Here's my advice on developing the skill.
In the AAU Volleyball magazine an article by Cassidy Lichmann lists five areas of the game where more work is probably needed. Here are my thoughts.
The Art of Volleyball Hitting by John L. Bowman is a quite thorough discussion of hitting aimed at players, but I think you can find far better resources.