The +spell damage modifier is based upon the cast time/recast time of the spell itself.
This is the actual equation that determines the damage it adds:
Item Spell Dmg value * (Spell Cast time + Spell recast time) / 7000
So example:
An item with 100 spell damage when casted with a spell that is 5s cast time and 2.5s recast would give:
100*(5000+2500)/7000 = +107 spell damage
An item with 100 spell damage and a casted spell that is 10s cast time and 2.5s recast would give:
100*(10000+2500)/7000 = +178 spell damage
As far as it affecting Procs, it does, but again the additions are based on the spells cast/recast time.
So some examples:
Kiss of Life II:
webtools/spell.php?id=9081Has 0 cast time, 0 recast time, so when you input it into the equation you get this:
100*(0+0)/7000 = +0 spell damage
Meanwhile, Lure of Flame:
webtools/spell.php?id=1638Has 4.5s cast time and 2.25 recast time, so when you input it into the equation you get this:
100*(4500+2250)/7000 = +96 spell damage
So TLDR answer:
The +spell damage on items uses a equation based on cast time/recast time of a spell and yes
SOME procs are affected by it.
Oh the fun you all are going to have in DSK3...
Simon says.. touch the green one! Nooooo BLIQUE NOT THE RED ONE! zomg you just got me "Vaion Touched"!