When it comes to spell haste, it seems blizzard is moving in this direction for casters based on all the new loot from ZA and badges.
With all the haste gear from ZA and badges I came up with 213 spell haste. (Dunno if I missed anything but if you feel up to it see what you can come up with). I looked around online and actually found the formula to calculate the casting speed reductions based on you spell haste rating.
New Casting Time = Base Casting Time / (1 + (Spell Haste Rating / 1570))
I'll use a fireball with the above stated 213 spell haste as an example.
X = 3/(1+(213/1570))
X = 2.64
If you're wondering where the 1570 comes from I'll explain that next. 1570 is the amount of haste it would take to reduce a 3 second cast to 1.5 seconds (GCD).
X = 3/(1+(1570/1570))
X = 1.5
That being said, 1570 is the "cap" on spell haste for 3 second spells. Of course spells like scorch or arcane blast would be well below the GCD at this point, BUT, since you can't bypass the GCD you would still have to wait until the spell is ready to cast again.
I figured with the addition of the Icy Veins talent I should do some number crunching to determine how much haste rating Icy Veins gives you while it's active. With 0 spell haste Icy Veins takes a 3 second fireball to 2.5 seconds. To figure out how much spell haste this adds up to you use the reverse formula.
Spell Haste Rating = 1570((Base Cast Time/New Cast Time)-1)
X = 1570((3/2.5)-1)
X = 314
Let's see what 213 spell haste with Icy Veins does to a fireball cast.
X = 3/(1+(527/1570))
X = 2.25
I also did some searching to figure out a rough answer to the question of which is better: Hit vs Haste vs Dmg vs Crit? From what I can see in most posts Hit > Haste ≈ Dmg > Crit. I found a really well written post by a guy on the Subcreation forums that I'll post below.
Note: 17 spell haste = 1.08%
Originally Posted by
Tiga from Subcreation
Given how hard it is to estimate the lag issues, I'll just equate 1 haste rating with +1 damage and consider that 15.76 haste rating will cost me up to 5 mana/5 (if everyone stacks haste or improves their DPS, the fight becomes shorter, so it doesn't work out as quite that bad in reality). I'll go a bit deeper into that:
If you have to do X damage in a fight and you have 10% haste, you'll do the damage in about 9% less time, which means your mana regeneration time is reduced by 9%. Things that fall into this category include mana potions, mana gems, mage armor, totems and the friendly neighbourhood shadow priest (although the shadow priest can possibly increase his/her mana battery efficiency if the main thank stacks haste and generates threat faster). Total mana used in a fight consists of your initial mana pool (around 10k average, I guess), evocation (7k after patch unless you have enough T6, up to 9k now). Assuming you do 10 damage per mana and need to do 400k damage, evocation and your initial mana pool will account for 170k to 190k of that. That means the other methods mentioned need to generate up to 23k mana somehow. Given 9% less time than before, 9% of 23k is about 2.1k. Assuming you have 9 minutes to dish out 400k damage (that's only 740 dps btw, but there's usually movement etc), the 2.1k mana regen over that time equates to 19.4 mana/5 seconds.
Based on the "paper napkin math above" (which is probably flawed in many ways, but gives some ballpark numbers to play with - and I'm wondering if I should post this at all), I guess 1% haste is going to eat up between 2 and 5 mana/5 seconds more.
5 mana/5 is based the assumption that your mana regen needs to keep you running indefinitely and 2 mana/5 is based on a situation where your initial mana + one evocation can be consumed and you end up with 0 mana at the end of the fight.
Source of Formulas:
http://www.wowwiki.com/Spell_haste
Source of Post:
http://forums.subcreation.net/viewtopic.php?pid=73006