So.....now Blessing of Leeches is the uber "My 1st-level cleric will kick your orc army's ass single-handedly" spell? Or "My 1st-level cleric is going to beat your 10th-level fighter into a bloody pulp" spell..... As it is, Fast Healing 6 or 7 would make the character extremely hard to kill without regularly dealing 12+ damage per hit (i.e. an ogre).... Perhaps Fast Healing 6, +1 per five caster levels, to a max of FH 10? That's the absolute most powerful I could see it being, and it's probably overmuch anyway.
Aura Barbs is cool but nasty..... By that level, any given spellcaster faced may have around 4+ spells active of 2nd-level or so, 1-2 1st-level spells and 2-3 3rd-level spells, and 2-3 higher-level spells, I'm guessing...... That's sorta like an "I dispel all your stuff unless you want to die instead?" Consider that a high-level wizard or sorcerer has abysmal Fortitude and hit points both...... Aura Barbs is something a 14th-level-ish sorcerer might face, so..... 10d6 damage or so is likely to kill him, unless he has high Con, in which case 14d6 damage almost surely will. Unlike against Fireball, the sorcerer can't just have a Protection from Elements (Fire) or Fire Shield active to save his fragile hide from certain doom. Stoneskin also won't help it seems. Nor Globe of Invulnerability, nor is Protection from Spells likely to be sufficient (and that's a 7th-level or 8th-level spell itself) because sorcerers have low Fortitude (though it might just barely be sufficient). Spell Turning just might, possibly, save his poor little butt once, and that's about it.
I'm not sure if a Wall of Force would, if placed properly, shield the character from Aura Barbs. I'd have to read up on how range and such work, to see if unobstructed line of sight is needed for this sort of effect as it's not exactly an area of effect. Resilient Sphere would guard against it I guess, though it requires sealing the character away so he can't affect the battle whatsoever.
I'd suggest that Aura Barbs instead deal 1 damage per spell level rather than 1d6 per spell level. Maybe 2 damage per spell level. Or something. But considering how there's almost nothing that will guard against Aura Barbs..... And the fact that not all spells with a duration are dismissable.
If you think I'm just being annoying or something, just ask me not to respond any further to this thread, I really don't care either way. I just think constructive criticism is better than letting abusable or worthless stuff get published/used unfixed.