Having run with the class before, yeah, it's pretty bad. If it were spontaneous it would be marginal, but as a preparation class it's well into the unplayable region. As it is, it seems like we turn to the healer and say "Did you prepare Remove Paralysis?" "No." "Did you prepare Break Enchantment?" "No." "Magic Circle?" "Actually, I don't even get that."
Other things like "Oh, I get an ability this level!" "Oh?" "Yes, I can
remove blindness/deafness!" "You're level nine. Is it at will or something?" "Nope, once a day.
" "
"
At least he can switch out the Unicorn for a Lamasu at 12. That'a free level 7 cleric. Then he gets actual clerical spell access. At level 16, you get a couatl, which is a free level 9 sorcerer.
If you want to make the class an NPC class, just remove the companion. At high level, the companion is the only source of power.
If you want to make the class a PC class, change the class to spontaneous casting with all spells known. Then change the Cleanse abilities to be like Bardic Music. You get a pool of 1 use per day per level, and you can use any of those abilities that you want.