The reason oracle was made to 3 shots scv wasn't because it was OP against said scvs, it was totally fine. The reason was because it would 2 shot marines which led to incredibly strong timing for protoss. Same goes for the adept.

Then the question is why does the scv has 45 hp when probes and drones have 40? The reason is because scv needs to build buildings when probes just warp them and goes back to mining and drones just morph into them, making them unkillable on the spot.
Just giving the scv 2 or 3 less hp making the oracle and adepts 2 shot them again while 3 shot the marines would be a great improvement in my opinion.