Just completed the mage tower on my Spriest, its much easier now imo. I brought drums and a flask. I used my M+ spec with tendrils and horror.
ShadowCrash like 1 shots the little adds, our damage and instant cast abilities make kiting a joke. For some reason our 4 set works atm. And our healing from our class tree is nuts for the burn phase. I did the legion version which is easiest imo. But SL felt overtuned. This seemed a tad too easy atm. But if you want the purple set id give it a go.
Same for discipline. It is quite easy now too, if you are, well, disciplined, with your CDs and avoiding bursts. It was a bit easier back in Legion, but only due to outgearing the challenge in later patch.