yes max out spirit tap. Saves you loads of downtime. Next once your are able to do low level instance, grab a good wand.
Bubble yourself, pain, blast(Think you should have by now- not sure been a long time since i played shadow). Wand, wand, wand till the mob is dead. if bubble goes off, bubble yourself again.
Once you get shadow form, it would be a breeze.
Hope this helps.
Cheers