While cure spells getting better as the caster raises in level makes a certain kind of sense, but doesn't adress why a cure light wound spell gets worse as characters advance. Granted a lot of this is simply naming convention, and if it hadn't been called Light Wounds this might not be a problem. But it is, and so it is.
So I'm kind of kicking this idea around, but don't know if I'll actually go for it.
The idea I was thinking that what should happen is this. Casting cure spells should be relevant to the power of the target, not the caster. So a clw will still be awesome to a 1st level guy, but as they get higher, it won't lose as much utility.
Cure I: 1d6+1 per level of the target (+0 for normals). Max of 1d6+4
Cure II (Moderate): 2d6+1 per level of target, max 2d6+7
Cure III (Serious): 3d6+1 per level of target, max 3d6+10
Cure IV (Critical): 4d6+1 per level of target, max 4d6+14
For a slightly more radical approach:
I: as above
II: as above, max 2d6+8
III: 2d6+2 per level, max 2d6+20
IV: 2d6+3 per level, max 2d6+42