Permanently enchant a Melee Weapon to have a 3% chance on spellcast to restore 100 mana to all party members over 10 seconds. Requires a level 35 or higher item.
The tooltip on the enchant says the proc rate is 3% however there is much debate about this. In game tests seem to show that the proc rate is actually 15%. It is interesting to note that once the enchant triggers its ability, it also activates a 30-second hidden cooldown during which time the Spellsurge effect cannot trigger again. There is at least anecdotal evidence to suggest that the internal cooldown was raised to 10 seconds in patch 2.1
This enchant is, in the extreme case, an average of 13.56 mana/5s for the caster's group. This assumes chain casting instant spells as soon as the hidden cooldown is over (13 m/5 if chain casting 1.5s cast time spells, since it triggers 1.5s later). In practice, you can expect to get less than that, possibly much less depending on your casting rhythm. Also, for shorter fights the proc timing will be much more variable.
Executive summary of TLDR example below: For fast low mana healing spells (ex Flash of Light), Spellsurge is better than +Healing. Especially see the Resto druid raiding guide for some discussion that may dovetail with this (for druid healing, anyway).
|Thoughts on the enchant by Mewt, of Frostmane US Server
Let's pretend in a boss fight, let's say, a paladin casts 1000 holy lights in a row (for calculations sake, let's pretend he started off with Light's Grace, so each spell cast was 2 seconds, totaling for 33.33 repeating minutes of constant healing (so let's pretend he has an unlimited mana pool, or at least tons and tons of mana/s))
In 1000 casts of Holy Light, if he ONLY had a +81 healing enchant on his weapon, instead of spellsurge, HL gets 71.43% of the total bonus because of it's quicker spell cast (2.5 seconds), so each cast gets 57.86 (rounded up) bonus. Multiply this over 1000 casts, and that's 57858.3 total health healed from the bonus alone, for a total of 2,378,858 health healed.
Now, if the paladin had spellsurge, theres no DIRECT bonus to healing added, but if the proc chance really IS only 3%, the enchant will proc 30 times after 1000 casts, and give the paladin 3000 extra mana. This means you get only 3 extra casts of Holy Light, which would be (averaged) 6963 extra healing from three holy lights. If there were TWO paladins spamming Holy Light, thats 13,926 extra healing, and then 20,889 extra healing if there were three casters in a group spamming holy light. Are there ever 4 casters in a group though? I don't think I'll list it in that case.
But what about cast time? If we have three paladins spamming Flash of light, in the time it took to cast 1000 holy lights, you could get 1333 Flash of Lights off. FoL gets 34.72 (rounded up) healing bonus from a +81 healing enchant, which means a total of 46277 extra healing from the bonus alone.
After 1333 casts, if only 3% proc spellsurge, You'll get 39.99 procs, let's round it to 40. 40 procs means 4000 extra mana, meaning 22 extra FoL's, which translates to 10450 possible extra healing done due to extra spell casts. 20,900 extra if theres two, 31350 for three, and 41800 if there's four, and 52250 for five people.
However, there's a debate going on claiming that the proc rate is 15% instead of the advertised tool tip of 3%. If that's true, then 1000 casts would get 150 procs, for 15,000 extra mana if you spammed a 2.0 second spell cast, and 200 procs for 20,000 extra mana if you spammed a 1.5 second spell cast. This means 39457 extra potential healing for Holy Light (this scales multiplicatively with the amount of people with the enchant, and if the spell cast time is the same), and 52725 extra potential healing done if you had ONE paladin with spellsurge spamming Flash of Light. If you had TWO paladins spamming FoL BOTH have 105,450 extra potential healing!!
But this all depends if the tool tip is correct or not. 3% seems awfully low, and statistically, +81 healing is the king, except in the case of where you're spamming a 1.5 second cast where you get less than half the healing bonus. Also, the awesome mana efficiency of Flash of Light helps.
So, in conclusion, if you only proc the spell exactly 3% of the time, it will only benefit the quickest of spells more than a +81 healing enchant IF one group has ALL five casters having Spellsurge, and using a 1.5 second or less cast time spell.
If you can get the proc to go up to 15%, then CLEARLY, with a quick spell, Spellsurge is much more beneficial than a static additive, like the healing enchant. Also, the fact that it helps all of your party members is nice too. But note, different spells have different amounts of mana efficiency, so the numbers can change dramatically depending on what spell you're using.
However, to basically sum everything up, apparently faster low mana cost spells reap much much larger profits from Spellsurge than slower, high cost spells.