That giant wisdom goes a long way in a lot of things, one of which just so happens to be an excess of practices which can used either to artifically lengthen a characters life you happen to die a lot or to increase they HP pool by a lot. And then there is also the resistance to poison/disease present in saurian. Thats huge.

Pretty sure that svirf rangers don't get any special perks for being in caves, they are just like any other cave ranger while in caves.

W-elfs are vuln to one of the most common materials in the game, that makes a huge difference in how easily they die vs saurian who are vuln to an element. I'd argue that your ability to not die at lower lvls as a saurian is higher than other races because its less common to find a vuln exploiting weapon for them pre 20 than other races.

Giant rangers also are worse at creep than a saurian is so its a give and take, also they are worse tanks so their leveling is slower which makes it harder to get to said bearcharge that can be useful.

Gnome and elf suffer from the same issue as w-elf, huge easy to exploit vuln. Sure you can master stuff easier but you still are gonna have to eat that vuln forever.

Human rangers are well, human rangers. Sure they have a few upsides here and there, but I think everyone knows why you dont see them very often.... They are just pretty bleh.