The creep change isn't necessary. Protoss don't have ANY of the creep problems terrans do. why? They make obs. I think the raven buff is fine, I don't think it needed one, but now that there is one people will flock to them like flies on !@#$ so we can actually see some builds around them and some mechanics developed to use them. But once terrans start building ravens, they won't be having as many creep problems.
Gas Cost it takes for Protoss to get an Observer.
Robo Facility - 100
Observer - 75
Total - 175
Gas Cost it takes for Terran to get a Raven
Factory - 100
Starport - 100
Tech Lab for Starport - 25
Raven - 200
Total - 325
I didn't include Mineral costs on purpose since we'd have to look at a Pylon, Supply Depot, etc.
But this should paint the picture.
Different races are different. If you bothered to read the post, this post is to address difficulties in TvZ, not PvZ specifically.
Observers are Perma-Cloaked units that are difficult to spot. Ravens are a giant flying Hit-Me sign in the sky.
The amount of Gas it takes to field a Raven early severely delays other essential Upgrades. It's not that easy to get Mobile detection early on as Terrans. Each scan used is 275 unmined Minerals, and it essentially negates the Terran's Macro ability and their only way of keeping up with the other 2 Races in terms of Resource Mining.
If the Terran is taking such a big investment/risk in getting a Raven, it should have some sort of guaranteed Utility.
The proposed change is very minimal. It doesn't address many other issues that the Raven has.
Among the others that have been proposed in this thread - The issue of Upgrade Compatibility and Scaling for Turrets. Infestor's IT and Broodlord's Broodlings both have Upgrade compatibility and scales well with Zerg's Weapon/Armour upgrades. These are all temporary units.
Raven's Turrets however do not. I never understood why they didn't link the Turret's upgrades to Ship Weapons/Armour upgrades. It's not as if we're asking to link it to Infantry Upgrades. A Terran player will have to go out of their way to get it, and it'll help Late-Game scaling.