*one*
Well I think the adjustments should different. I don't know about the changes that Two is suggesting. On the one hand they do make sense, but the other I am a little concerned about doing so, especially if it ruins the flavor of them.
I happen to think perhaps for the Assatthi instead of casting spells, they get spell-like abilities and the ability to use arcane scrolls, and arcane spell trigger items (like wands, staves, etc), to make them decent spellcasters still. To completely remove that aspect of the Assatthi I feel ruins the flavor.
Now as for the Dex bonus, I agree that a +6 is kind of high. But that shouldn't mean you can't make a variant or at least a "normal" breed Ratman/Slitheren that's usable at +0. The way I'd do it is probably keep the +4 Dex and +2 Con, but also give them say a -2 Str, Int, Wis and Cha. That way they can still be usable without being totally ridiculous.
The Proud...are something I think needs work, but again I'd probably lump them in with some higher level monsters, especially since they can cast spells. They'd be more likely to be in higher level games.
Gnolls, goblinoids, and some other MM monsters with low to none +0 LA/ELC should be consider as part of the norm more than the Proud, more than Hags certainly, and probably more than most titanspawn.
Indeed I am considering specialized human like race that are natural sorcerers, much like a lower level version of spellweavers. I wonder if anyone would be interested in that.