*cracks knuckles*
It's about damn time! I think maybe I'll spend some time number crafting to work Frozen Core into my spec (I would at the expense of Brain Freeze but that would suck once you hit 2PC T10).
You can look at my mage, Versi, on Sisters of Elune, for the current best frost spec.
It looks like Blizzard is making Ghosted Ice Lances part of the normal rotation. When fingers of frost procs, you can cast 2 frostbolts, then at the VERY end of the second frost bolt cast, you can cast either Ice Lance or Brain Freeze. According to the PTR notes and T10 info, this will depend on if you have a Brain Freeze proc available, and we may still end up ignoring Brain Freezes with this change.
The 2 Piece bonus is that if Brain Freeze proc is used, it grants you 12% haste for 5 seconds. That's 12% haste for around 3 frost bolts ignoring other haste procs.
Taking 1 second off of Frostbolt IS more important, as that brings a frostbolt down to around .8 seconds. This, however, bumps against the GCD of 1 second (at the amount of haste it requires to get a 1.8 second frostbolt.) .216
12% haste will make it around a 1.6 second cast (1.584), but that won't bump the GCD.
Very interesting, and much to test out.
The Water Elemental change, however, is a raw DPS increase. The Elemental does a good amount of my DPS (10%?) and he's only up for around 1 minute out of a 5 minute fight. If my DPS is 5K, he did 500 DPS. If he's doing that, times 4, he's doing around 2K DPS (Oh I feel like I'm doing that wrong, please correct me if I am). THEN you factor in the fact that in a fight where he's out for one minute, he's wasted two global cooldowns. My GCD is at around 1.5 seconds, which is almost an entire frostbolt.
Since he gains stats dynamically already, buffing him isn't an issue, and he gets all of my buffs added to his damage. It's also worthy to note that he's almost immune against AoEs, so he's ALWAYS doing damage, sort of like a very powerful DOT.
Testing to follow.