The fact that your current reasoning leads you to such ludicrous conclusions as to believe a mid-end attack from Loki is superior to two Bajrang Guns, should be the first glaring indicator that perhaps you've gone wrong somewhere.
You are not currently acknowledging that Loki hit a defenseless Harald. Roger and Garp had to take down a fully defending Joyboy level character. Their feat is vastly superior from that perspective. Defenseless Oden was killed by a bullet. Defenseless Roger was killed by two fodder swordsmen. You are not acknowledging that Harald had absolutely no defense.
If it turns out that Loki's ability to kill immortals is a by-product of his DF, then you have vastly overestimated this feat. Even so, the only reason Roger and Garp struggled against a Joyboy level character was because of the CoC barrier. If Xebec took the CoC barrier down and laid himself bare like Harald, it would not have taken their absolute strongest attacks to put him down. Rn you're doing 2+2 and getting 22.
Imo you're falling for the trap of nitpicking flashback feats and missing the bigger picture.
You and the people calling Loki “god tier” are actually two sides of the same coin right now. One side hyperanalyzes to poke holes in everything, while the other hyperanalyzes to conclude he can solo Prime WB + Garp + Roger combined.
The narrative is clear to me: Loki > Harald. How Oda got there, or how much exaggeration he used to sell it, doesn’t really matter to me at this point. I don’t believe Oda’s intent is for Loki to be below Harald after obtaining the fruit, he did far too much setup for that. We should be past that discussion by now.
What really matters is that being clearly above Harald is something even Xebec never had. That’s the real issue here, and that’s a major part of the reason why Imu was so shocked, and why Gaban thought it was over for the verse. An apex top tier is what Harald was.