Why? Why does the searing light SLA share a cooldown with searing light SLA you get from cleric's disciple tree? Why is this the only domain that gives you an SLA of an SLA you already possess? Not only do you do this, you also nerf sunburst and sunbeam's blindness effects in the process. At best, you get 3 extra AP from this.
So, what could go in place of the searing light sla? I thought of a few quick ones:
Scorch SLA. While scorch is a fire spell, the sun domain also gives fire spellpower, so it fits thematically. Scorch would give better aoe damage in the early-mid levels where cleric is severely lacking in aoe capabilities. This also doesn't step on the toes of any other class, since sorcerers get the scorch SLA around level 5-6 in the fire savant tree, as well.
Sun Bolt SLA. I'm not sure why this isn't here, in the first place. It's a level 3 cleric spell, anyway, which clerics can get in the disciple tree. It also ties in with the double spell range that light-focusing cleric tend to have. To balance it out, I'm sure an 8 second cooldown would be fine, given its comparative power to searing light and its 4 second cooldown. It's not like this is comparable to lightning bolt, either, since sun bolt doesn't have a chance to hit twice.
Blindness SLA. While not my first choice, it fits thematically and allows for a cheap debuff for bosses, champions, etc. Power Word Blind would work, as well, but that's a bit much at level 5.
Turn undead regeneration. If anything the sun domain symbolizes, it's anti-undead. Why not give the sun domain automatic turn regeneration, which would stack with what you can get in the radiant servant tree and later in the divine crusader tree? This would set the base 2 minute regeneration rate, increasing by 30% with radiant servant and 60% total from divine crusader.
Light damage toggle. Just like you find on items like the lantern ring or resonation necklace, give a small light damage bonus on every offensive spell cast.
Light critical chance. A flat +3% or +5% critical hit rate with light spells would be a good fit, here.
Light resistance. A simple +1 light resistance per cleric level or +1% light absorption per two cleric levels would be interesting. Couple it with blindness immunity.
Thoughts?