The main problems of both Classes are that they are underwhelming Rank 6+ Classes.
Instead of performing greatly for the Ranks they occupy, they only do things half-assed (e.g. Prophecy only prevents Rank 1 ailments while Bloodletting prevents Rank1+2, Foretell only has a 55% chance to avoide damage while Sterea Troph avoids all damage, Counterspell only has 1/3 uptime in contrast to Safety Zone/Sterea Troph that have more than 1/2 uptime, Ein Sof still relies on healing/recovery skills while Healing Factor heals you when you get damaged, Merkabah is one of the worst Rank 5+ damage skills in history[only surpassed by skills like Indulgentia and Decatose] and all number-related skills are badly designed).
That’s why they fall off especially hard when it comes to Rank 8 content, having to rely on lower-ranked skills most of the time to deal any damage at all.
While Kabbalist still has hope because of C3, Oracle seems to be dissed hard by IMC because instead of balancing the Class,it was even nerfed.
The reason is that the HP and defence reduction benefitet all Classes except Oracle, as Oracle had an advantage since it’s skills ignore defence and are more effective against monsters with more HP.
Now Oracle is dead last because it’s skills aren’t affected by your atk/weapon and have too much CD time. IMO even 5 overheats with 10 seconds CD time on Death Sentence wouldn’t be enough to rebalance the Class enough to become a “good choice”.