Pielorinho, I think your solution should be not to change the spells themselves, but to enforce the limitations that already exist.
I don't know where you got the idea that Blindsight grants X-ray vision; I don't recall seeing that in the spell description. That's #3 on your "nerf" list, but it seems clear to me that the spell wasn't intended to grant that ability in the first place.
You say that Darkness effectively makes everyone in the globe invisible, but that's not the whole truth. It also makes everyone OUTSIDE the globe invisible to those inside! In effect, they become invisible but blind. The cleric with Blindsight can see, but anyone else in the globe is completely SOL.
Also, the darkened cleric will be unable to see more than 30' away. If I just move 30' away from the cleric and then 30' in a random direction, he has no idea where the hell I am. If he tries to follow me, he'll need to guess which way to go; a wrong guess will just send him even further away.
In addition, the centerpoint of the globe is apparent, so enemies needn't guess where to aim. Ranged weapons will only suffer the 50% miss chance from concealment, and area attacks won't miss at all.
This all has been pointed out before, but it bears repeating. If you're not enforcing the limitations that already exist, why bother adding more? If you allow a 20th-level wizard to throw Fireballs for 20d6 damage, that's obviously unbalanced. But don't nerf Fireball to 1d3 per level; just enforce the 10d6 limit that it already has!