I still think making the entire dungeon a wild magic zone would do much for this, as it doesn't completely gimp casters of all sorts, casters just have to think more carefully about what they're casting, as their higher level effects are more likely to go completely awry and it's hard to optimize to resist the effect (who seriously has a build that's specifically resistant to wild magic, really? Unless Wild Mage has built in resistance, i'm not seeing it). Plus, given the kobolds have probably been the area for a long while and have inured to the effects somewhat, you could give their casters a bonus feat, such as either of the following:

Resist the Wild
You've spent some time in a wild magic zone and have learned to somewhat overcome the chaos to cast successfully more often.
Prerequisites: Live 3 months in a wild magic zone.
Benefit: You get a +4 bonus on level checks made to overcome a wild magic zone's effect.

Embrace the Wild
You've spent some time in a wild magic zone and have learned that by taking in the chaotic magics, you have more control over the effect they have on your spells.
Prerequisites: Live 3 months in a wild magic zone.
Benefit: You cannot resist the effects of a wild magic zone. However, when you roll on the wild magic table, you may adjust your result up or down one category. For example, if you rolled at 67, you could choose instead of not casting the spell without expending costs to cast normally.
Normal: You can resist the effects of a wild magic zone but what you roll on the wild magic table is the effect you get.

So, either you go the path of boring "I'm more resistant to Wild Magic Zones!" (probably the path taken by clerics of Kurtalmak) or you can choose to have a bit of control on what you get, especially that Spell Enhancer effect on a 99-100. =3

Them's my 2 coppers. Take as you will.