The change to CoC is a nerf

The change to the mana multiplier (120% rather than 140% for attacks and 100% for spells) is a nerf and should be reconsidered unless GGG's intention is to nerf the gem.

In general, attack skills have lower mana cost than spell skills. This means that the mana cost reduction (140% ->120%) for attacks have little impact on the total mana cost of CoC. For example, let's consider a coc setup using cyclone. A typical spell has a base mana cost of 24 at level 21 while cyclone has 2. Thus, 24/26 = 92% of the total mana cost is from the triggered spell, assuming 100% crit chance. As long as a player uses cyclone to trigger spells, the new change increases the total mana cost of the CoC setup by roughly 20%.

Of course, not everyone uses cyclone with CoC. But other options such as barrage, tornado shot, and rain of arrows trigger spells multiple times per attack, again making attack mana cost irrelevant.

If clarification of the mana multipliers on CoC and related gems is the purpose of the change, please consider making it 100% or 110%. If, on the other hand, the purpose is to nerf CoC, I don't mind it but would like you to state that in the patch notes.

+1

I am SURE the purpose is both nerf and clarity. Considering the absurd multiplier attached to cast when damage taken they probably thought having no extra multiplier attached to spells was too OP.

I am equally sure they would never directly say "we want to nerf CoCS further". They worked incredibly hard disguising the fact that 90% of the changes are either nerfs or partial rollbacks, rather than buffs as they describe.