Let's recap first. Disclaimer: All translations to English are mine and therefore can be off.
Forta impreso farita sur la psikon, precipe de belarta verko, spektaklo ks: kia granda efekto ĝi estus! "what a great effect it would be!"
Faranta konsiderindan efekton: grandefekta revuo, "a review/magazine with a great effect"
I couldn't find anything either for reive (nor reave), but the word
comes to mind, which with rab/ expresses the looting of cattle or goods and with atak/ the suddenness and violence of it. There are also sereval entries in Tekstaro of forms of this word.
So reiver would be rabatakanto or rabatakisto.
It's unlikely an established Esperanto word for this already exists. I'm unsure what exactly characterizes a "grook" and thus whether it can captured by a kunmetaĵo that is both sufficiently concise (i.e., short) and also sufficiently precise (to avoid confusion with non-grook types of similar sorts of poems or aphorisms).
If "grook" just means "aphoristic ...