I'm trying to preview how a specular material looks on an object when it moves, so I tried rendered viewport shading mode, but this mode is extremely slow even with a very simple object. So slow that if I play a simple rotation animation nothing draws to the screen. I'm running an i7 with a GeForce 730m, I feel like I should be getting better performance than this. Am I missing something here or is it really not possible to preview an animation with materials without rendering a video?
Rendered shading is the same as a final render (mostly), so unless you have a very simple scene and a small render farm, you probably aren't going to get even near real-time (as in > 1-2fps) renders.
Some things you can do to help:
Render a small low resolution part of the viewport (e.g. with render border) See Render Border's related check boxes - How do they work?
Reduce the number of samples (Render settings > Sampling) and bounces (Render settings > Light paths)
If you still want to use the viewport (though I would recommend rendering a quick image sequence), turn down the framerate so each frame has some time to converge.