Spirit bond healed me more than enough to get through infests. Necrotic nerve should be at more the the initial stack - use glyph of misdirection to keep all adds on pet, make sure necrotic falls off you at range.
As for valks, I just kept tunneling damage into LK through the intermission, saved Stampede etc. He never even went into p2. Once you get to second intermission at 40 percent, you can go to the edge and heal up via spirit bond and just dps images.