You want surge up to 30% (this is where diminishing returns starts hitting hard), then power, then crit. Scream is going to be the bread and butter of your attacks. It will probably be the top% of your damage (once we have combat log it can be confirmed).
Surge will make your scream hit as hard as possible.
Power will increase all of your damage.
Crit will benefit all non-scream attacks, but overall those attacks will be less damage than scream.
If you can pull off 30% surge and 30% crit while not sacrificing power for crit, do it. And as you said, get as much str as possible.