WRED at the interface level might normally be exclusive with a service policy, unsure, because it might vary based on platform. The router should preclude you from doing so if unsupported on the platform.
Do keep in mind, you can often use WRED within a policy class, which is often a much better idea. For instance, in your post, it might not be a good idea to use WRED on your ROUTING or VOICE class, but perhaps good for class-default.
PS:
BTW:
If you're thinking, with WRED you could adjust the DSCP weigths to treat ROUTING and VOICE different from other classes, certainly, and that's what you might need to do further downstream if just using WRED alone, by why subject all traffic to such QoS when there's no real benefit to do so (i.e. when you're using a service policy).
