It is an expensive build, but if you get full build your ulti will heal for 1k and your Blessing will heal for around 800. The magic pen makes it much easier to harass the team back at early/mid geme. If you were going to change these for anything I would suggest cd reduction, but the Magic pen is just my personal preference and I will add this to the guide.

The build seems very expensive, and why would you want 15% magic pen? your not doing damage, no real reason for it