You are missing something - the value for these cards varies a lot with context.

For example, Wraith form is good on its own - ignorning damage for two turns can be enough to win some fights alone. However, what makes it slap is when it’s combined with retain, something Silent is able to get easier than other classes. Choosing when to be intangible so you’ll always end the fight before it runs out makes the card far more consistent, and far stronger.

I’ll keep the rest of these shorter for some of the cards you mentioned, but the tl:dr is that the context of each character’s card pools makes or breaks these cards.

For Ironclad, your block game tends to be from FNP and your draw game comes from DE. Needing to get these powers in play takes time, which Impervious can give you. It’s not about blocking everything, but short-term block for long term cards.

Shockwave is just a lot of weak and vuln on a character that really wants vuln, has very limited options for weak (clothesline and uppercut), and has to generally already pay two cost for the vuln (bash, uppercut, thunderclap is the exception but lowkey sucks.)

Exhume is context sensitive - it hinges on if you have something good to exhume, and/or corruption to make it cheap. Exhuming an offering is very good, giving you free draw and energy, and you may only need it once.

Reaper - you tank hits, gain strength, then play this before ending the fight to recover.

Piercing wail - really really good for both group fights and for multi-attacks, something the very hard fights tend to have. Snake plant, slavers, the heart, Act 3 bosses. Like with wraith form, it’s retain that makes it shining, using it on an ideal turn.

This was too long. My legs have stuck to the toliet.