Damaged soul =/= insta dead in Nasu. Old wormy Matou has his soul literally rotting away and he stuck around for centuries anyway. ROA also took time to die even as his soul burnt away. Getting poked by her sword or feeling her flames won't kill him.
Servant souls are also worth thousands of times more than any human, and if Enkidu's is remotely comparable to Gilgamesh, which they should be because they are equals everywhere else, it's worth hundreds of thousands of normal souls.
Yes, their weapons hit at both a physical and spiritual level. Guess who else does that?
Guts. That's not a straw man either. It's an explanation of how a weapon that can damage souls still needs to actually damage the physical body to damage the soul. Kei's weapon can hit on both levels, but if the physical level blocks her sword before it can actually cut the spiritual level, that won't soul hax. The explanation page explicitly says it can be
blocked on two levels.
"Even a spirit without a body would be cut down" - no shit, their weapons hit souls after all. But if the physical body stops the weapon from hitting the soul in the first place, that won't help.
Well, it isn't like there are any other gods in the Masada - oh yeah, Methuselah. Ok. Bad example. What I was getting across was that them killing "god or demon" and "nothing could nullify their strike" are hyperbole and/or an unexplained NLF.
Haven't got scans, but the Grail works by using an incomplete heaven's feel (soul magic) to pull down a piece/copy of the heroic spirits soul and manifest that soul as a servant. And "incomplete" means "not the perpetual motion engine they wanted" because it still takes a master's mana to hold them in the world. Not because it isn't their actual soul. So yes; servants are fundamentally spiritual beings, and Kei smacking his soul is the same as her smacking his body - blocked by his dura