The murder of Ellie puzzles me from a storytelling standpoint
It shouldn't - It was admittedly heavy-handed but an effective narrative device that establishes the scale of the threat very clearly and concisely. He went to all this trouble to introduce and establish Ellie and then make us like her (and establish that she is someone Pate knows and does business with personally). Then he had her brutally and savagely beaten to death; then he had Pate stand in a pool of her blood and wave this off as 'shit that happens'.
Jeph has just told us just how dangerous Church is and just how amoral Pate is. He's also told us that no-one is automatically safe, no matter how well established the character.
I probably should have gone into more detail, but I'm rushing today. What you say is true, and that's understandable. What I meant is that Ellie herself was not neccessary to be used as the blunt instrument. She is the leader of this group. We have seen others - the gent who told her Pate was there, and the background peeps in the bar. It would have been an interesting tableau if, instead of Ellie, one of those other people had come to Sedna's aid. They still would have been just as mangled as Ellie became, and everything you mentioned in your post - Lurch's deadliness, Pate's sociopathology, the real danger that Alice feared - would have been established. The additional deal, though, would be Ellie's survival. To this point, she has seen Pate as a benefactor. He seems to travel with Lurch exclusively. Pate has come and gone from the community without any issue. Sedna is a friend/acquaintance who, we are told at the start of this arc, had not been seen at the community since they seemed to stop running into the guns she collects. Ellie likes her, but it is Pate who helps keep the community running by providing it with the goods and services it needs to carry on its work. So it's Pate that is the important one, in Ellie's view. And Pate - up to now - has show no signs of being a bloodthirsty maniac.
Had one of Ellie's people been killed, then Ellie herself would have been in a quandary. To my knowledge, she is never told by Alice or Sedna about their fears of Pate, so if one of Ellie's people had been killed by Lurch, then to save the rest of them, it's possible Ellie would have felt compelled to sell them out to Pate and offer up what information she gleaned from Ardent, Sedna, Alice, or all of the above.
But killing Ellie herself likely means that this community won't play a very large part in the narrative going forward. Save for Jim (?), the young boy we meet at the very start of the comic, Jeph had not introduced a person who had a substantial speaking role beyond serving as a punchline who did not end up playing a large part in the narrative. We had Ardent, then Gavia, then Sedna, then Ellie. Ellie is now dead when I assumed that whatever else happened, she would be a large part of the story going forward. So it just puzzles me, but not in a bad way, just in a "Huh, that's not what I expected" way.
I wasn't knocking on Jeph or the way he is choosing to tell the story, if that's what you inferred. It's just that I foresaw Ellie playing a big role, particularly when it became clear that she knew and liked Pate. With her death, those avenues are closed. Interesting choice.