Yes, some stat effects are on tiers, but there are also more applications
of stats then you are aware of. The obvious difference between 17 and
18 wisdom is 2 vs 3 practices, you may not know (as a fictitious example),
that the 17 dex (storm war) vs 16 dex (fire war) relates to a +5% chance
to dodge. That sort of stuff would be behind the scenes. You see the
tip of the iceburg, while you ignore the bulk of the iceburg.

Why the hell are you contrasting vuln wrath vs vuln fire? For the sake of
simplicity, we're talking about giants. No giant is vuln fire. Compare
apples to apples (giants to giants), and storm giants are clearly head and
shoulders better then the rest. The only thing I can glean from your post
is that cloud giant vuln is nicer then the fire giant vuln.. WHOOPIE.

You want to stack two giant warriors against each other? Fine, grab your
fire giant. I'll grab my Storm with a cold damage noun.
A fire giant with +1 str, and +2 con compared to Storm is not going to make
up the deficit for having a vuln. I'll take as much INT, DEX, and CHA as I
can take. They're just as good as STR and CON, even for a fighting class.