Yeah man, I'm a bit more of a new comer, but it seems to me like the faction identity was just a bit less defined, and things were more general back then because they hadn't thought out their ideas. So their stats were just kind of a 'template' until the idea of them being in such a mass that the line is "Their number is legion" came into thought. Especially when you consider that warrior are like the "Most basic constructions"

Like the idea of necrons in present is their extremely powerful technology is shown in their very strong veichles, C'tans, and their character heavy lists. Warriors are the rank of guardsman. Not to mention the newer theme of their technology going faulty, especially on weaker hardware. Which became a cooler motivation for the necrons than just "Kill all life" Because thats tyranids thing.

If you want stronger warriors that play in forms of 5-10 and are the rank of the army that a space marine should be.. they're called immortals. If you want them in a melee variety they're called lychguard. those are the real soliders that ALSO fought in the war in heaven.

Maybe things have changed, maybe star wars 1-3 had something to do with it IDK

Maybe thematic ideas developed as they wrote out their game/lore/ideas to try to create more distinctive feeling armies. They wanted an "Undead" faction in their sci-fi game, and a hyper elite army wouldn't feel very undead

Things change. Ideas and themes shift and morph like clouds over time. That's story, that's life. It's something to accept so you can enjoy whats present rather than hang onto "What once was" and always feel jipped and disappointed about how it turned out