71 skill points still unused, so 23 in Search, Disable Device, and Gather Information is more than reasonable. Since Tarrasques are no longer an issue, he could, indeed, trade those scrolls for a +4 Str item, since penalties like that from Exhaustion are not uncommon. A Belt of Battle would also be rather reasonable, since extra actions are good on literally everyone (effective, perhaps not, but everyone can make use of them).
Step 1. Kobold must be going to the shrine for some reason. A result of 35 on his Gather Information (taking 10) will definitely alert him of a guardian, and a powerful one at that. Exact details may possibly be fuzzy, but he'll know that whatever it is has magic and potent magic at that.
Step 2. Upon arrival, the Kobold stakes it out for a bit. He would notice any summoned guards and would even notice them blinking out and being replaced (twice) with a simple 5 minute observation. Thus, whatever is guarding the shrine (at this point, still directly unnoticed, though he might pick up the orders being given, since the Solar is not telepathic) is clearly capable of summoning, and very, very frequently. Since Kobold cannot see the summoner, he would activate his eternal wand of See Invisibility for 30 minutes of seeable-Solar.
From there, it's child's play to avoid the "patrols" (Detect Magic requires 2 rounds of staring at the same spot to get any real information, and this Solar has likely dropped spells like Continual Flame all over so "presence of magic" means nothing).
Step 3. Since the Solar is still unaware of the Kobold (it literally has nothing that would allow it to detect the Kobold), the Kobold finds the (still invisible) Solar (recall the kobold can see it fine thanks to See Invisibility). Kobold then waits until the current patrol is just about to expire (timed thanks to the 5 minutes of observation) and unloads a full volley into the Solar, downing it. The Avoral vanishes before being able to help.
If the Solar was smart and had the summons on a much more frequent rotation (such as having two up at any given time, usually having three), then it would, indeed, be a bit trickier. He might invest in an anti-summoning scroll (or even more likely, a Belt of Battle so he could down the closest Avoral too). Any remaining Avorals (two more I might consider plausible) still have no idea where the attacker might be, and neither does the Solar (since it was knocked unconscious). Now, what does the Solar do? It has half it's normal HP remaining and has no idea where it got attacked from. If it summons another Avoral to heal it, great! The Kobold just burns him down again with another full attack. He can keep this up nicely until there are no more Avorals to heal the angel, at which point he just stabs the unconscious angel over and over again for the next hour or two, at which point he has plenty of time to go through the shrine for whatever he needs (The Solar is down for a day or so, since it's effectively 16 rounds for the Solar to regenerate each single round of Kobold stabbing, then it has to heal the Str damage, which admittedly won't take it long since it has Heal prepared).
The Solar would not have Obscuring Mist as a defense unless they had already managed to detect the Kobold because that is not an at-will ability. As such, since it only has a 20 minute duration (less dependent on wind).
