Wilder might be the "worst" 9th level caster class.
Worse than Healer or Battle Sorcerer? I'm not necessarily debating, but curious if those were included in your comparisons.
Well, I don't know those 2 classes at all.
But if you compare the Wilder to say an Adept (ouch).
The Adept has many more ways of expanding it's spell list, and then UMD the good stuff.
The Wilder gets less "spells" known, higher access without needing UMD, and then a better stat base, to UMD the rest of it.
The Wilder also has to invest feat slots or
something to fix enervation.
Don't get me wrong, a Wilder is stronger than an Adept, but you can't compare a Wilder to any other 9th level caster.
Unless you do something like, a Cleric with just 1 Domain, no regular Cleric spells.
You'd still have better class features, and more expansion options.
A poorly built Gish Sorc that still has 9th level casting, is far superior; and that's not good.
Wilder is either strong Tier 4, or weak Tier 3.
Wilder with a PP recharge set-up, is slightly stronger than Warlock, with maybe a smidge more options.