3.8Self cast Ball Lightning Hierophant - 14k ehp, 12kehp/second, 8 million shaper dps

I do play some kind variation of this build in Metamorph league. You can check my profile. Traded some damage for block to get more tanky. Overall this build is very good.

I'd say you need at least 15 ex to handle T16 metamorphs and endgame. 12 ex for Watcher's Eye is reqiured to sustain ES. You'll get one shotted pretty often without it. 4 ex for one 6-link. 2 ex boots. Other stuff is not expensive but I've aimed 1 ex for each slot.

This is not insta phase damage build so need to avoid some big hits. Still I die occasionally. Did not kill first Sirus because lured storm to the entrance :) Shaper/Elder Guardians can be face tanked. Awakener Guardians can be dangerous (the poisone one and cold one). Had no chance to fight Shaper nor Elder yet. Need to take care of metamorphs with corrupted blood or caustic ground because you'll die fast once stop hitting after boss is killed.