I watch a lot of professional SC 2 and the game is in such a nice spot right now balance wise, with a mix of strategies being effective. Hopefully with these changes the good spot the game is in now will only get better.
How about fixing the f'ing Widow Mine? You know, the OP unit that:
is fairly cheap
has a huge AOE explosion
automatically fires by itself
has a ridiculous long range for a mine
never misses and can't be dodged
does absurd damage
doesn't die when it explodes
These things are a pain to deal with when they're used to defend, but Terrans bring them with when attacking and they're impossible to even find in the middle of a chaotic fight.