so i was thinking about hte mana regeneration changes, who they will effect, and how so.
so, i'll start with mages, and continue from there. frost mages are getting replenishment (and a nice one) from their frostbolt. they never ever ever have had mana issues (have you seen how little a talented frostbolt costs to cast?).
fire mages will see about the same amount of mana regen.
arcane mages will se a reduction by 25% of while casting mana regen. how? easy. lets say today you (as an arcane mage) have 600 mp5 (from spirit) base (raid buffed). you were running glyphed mage armor, for 80% mana regen while casting. thats 480 mp5 while casting ( from spirit).
reduce 600 by 40%. that gives us 360 mp5. 100% of 360 is.... 360 mp5. that is a 120 mp5 while casting loss. 120/480 is 25%. in a AP burn phase, an arcane mage is using 2000 mp5 or 400 m/s. a geared arcane mage (today) has about 750 mp5 while casting, so 150 m/s. that gives 112 secconds before oom. with the changes, that puts us oom at 102 secconds.
it basically comes down to 10 less secconds (thats 50k damage) per evocate cycle. in a 5 minute fight, thats between 150 and 200k damage lost. however, we'll adapt, and reduce the mana usage, but dps, so instead of 5k dps, it'll be 4500. 1.35 million (give or take) on a boss fight. that is opposed to a 1.5 million in the same 300 secconds. so, 150k damage. this is assuming you don't get your evocate cut short.
this mana change, for an arcane mage? it means a 10% damage reduciton (it'll end up being more like 5%). however, that is in todays gear. as we get more intelect, and larger mana pools, the issue won't be as large. arcane mages had better pray for piles of int in ulduar.