SC:R is nearly perfected balanced (among top pros at least) except for PvZ early stage when the Zerg 9734 (a tactic with Hydralisk to give Protoss enormous pressure in early game) could easily overwhelm Protoss. Even if Zerg couldn’t directly kill Protoss early on, the economic edge is built for the Zerg.
The only change needed to make PvZ balanced at early game without impact on later game is : “Grooved Spines” now an upgrade option for Hydralisk after Zerg upgrade to Liar (like the “Lucker Aspects”, currently GS can be upgraded while Zerg’s base is Hatchery). This change will make Protoss more defensive against Hydralisk in the early game without making mid-late PvZ imbalanced.
For PvT and TvZ, the current state is good enough, and trivial imbalance could be adjusted by map changes.
Hope Blizzard could seriously consider my suggestion, thank you!