While I agree that Soa definitely has its share of annoying bugs, nearly every one I've encountered can be dealt with and should not interfere with the boss being killed. My guild spent 11 hours trying to kill NiM Soa before we got our first kill on 8man. During that time, we learned how to deal with his bugs and have been one-shotting him since.
To OP- Like others have said, the boss despawning in the last phase can be corrected by having someone taunt during each mind trap.
Regarding pillars not hitting the boss- We have had attempts where he gets hit by the pillar, goes through the animation of getting hit, but does not lose his shield. Because of this, the biggest thing I can emphasize is being consistent throughout his last phase. He will most likely enrage if he misses a pillar, but that does not mean he cannot be killed. Soa's enrage on 8m NiM is a complete joke and is barely different than his non-enraged state. If your raid is wiping as he enrages, it is because you are not dealing with the other mechanics properly (lightning balls, breaking mind traps, not getting hit by pillars, etc.).
I hope most of these bugs are fixed soon but making a post complaining he is impossible to kill isn't the way to approach Soa. Good luck!