Adding the scourge is actually a good idea. Imagine Muta/Scourge/Ling battles just like in BW, and neither zerg player goes beyond lair tech and hardly take a 3rd base.

Inasmuch as Blizzard wants SC2 to be just as epic as SCBW was, they will not add back the SCBW units, which in my opinion, is better because SC2 is a similar, but entirely different game from SCBW. And I don't want SC2 to be an SCBW clone. SC2 is already epic in its own way.

I think the spore crawler buff is actually good. Roach/Hydra vs Muta is now somewhat viable as the player who goes roach/hydra could leave 3 to 5 spores per base (plus the queen) to defend against muta harass and still mount a considerable offensive. Of course, getting a critical mass of +1 mutalisk (and proper micro) could negate the spore crawler buff.

Crunching the numbers off my head, if I could get 30 mutas with +1 attack, and properly engaging each of the spores (to take the least amount of damage possible), the mutas would take 2 volleys in 2.5 real world seconds to kill one spore. So a base with 5 spores and a queen would still take less than 20 seconds to fall.

So this change only provides you benefits in the early-mid game, around the 11 or 12 minute mark when the opponent could make around 12 mutas as soon as his spire finishes. But again, it will not deter anyone from going for any mid-game muta builds (the mutas can still be used beyond just mineral line harass).

On another note, this buff just solidifies my belief that the non-mirror match-ups (ZvT, ZvP, and TvP) are balanced.