With that Tarot class, maybe rather than making it just a random-spell class, you could make it a "prediction" or "fate" class.

It could focus on success and fail rates of targets' attacks, allowing it to become both a handy disrupter and enhancer. If well-implemented, it could even provide the user with warnings of when the enemy will launch major attacks via passive abilities.
(Ok, I confess, I'm thinking of Xenoblade here...)

Each tarot card's weapon skill/spell could produce a different effect, such as the following.

00 Fool - Self KO and auto-raise with weakness (allows self to reset hate).
01 Magician - Maximises the potency of the next offensive spell used by the target.
02 Priestess - Maximises the potency of the next restorative ability used by the target.
03 Empress - Maximises the resistance against the next spell used on the target.
04 Emperor - Maximises the resistance against the next weapon skill used on the target.
05 Heirophant - Transfer a random enhancing effect from your target to yourself.
06 Lovers - Transfer a random enhancing effect from yourself to your target.
07 Justice - Temporarily cause the target's cooldown timers to move at half the speed.
08 Chariot - Temporarily cause the target's cooldown timers to move at double the speed.
09 Hermit - Reduces the target's emnity towards their own current target.
10 Fortune - Maximises the accuracy of the next spell or ability used by the target.
11 Strength - Maximises the power of the next weapon skill used by the target.
12 Hanged Man - Minimises the accuracy of the next spell or ability used by the target.
13 Death - Chance of instant death on the target
14 Temperance - Halves the remaining time of debilitating ailments.
15 Devil - Minimises the resistance against the next spell used on the target.
16 Tower - Minimises the resistance against the next weapon skill used on the target.
17 Star - Transfer a random status ailment from yourself to your target.
18 Moon - Transfer a random status ailment from your target to yourself.
19 Sun - Increases the target's emnity towards their own current target.
20 Judgement - High MP use, high damage, long cooldown attack that attacks the target's elemental weakness.
21 World - Resets hate for the party (long cooldown).