Okay, so the new veterancy change is essentially this:
1. All units assigned a value based on their tech level. 1/5/10 for T1/2/3 units.
2. When killed, units give this value of points, rather than 1.
One would reasonably anticipate that units who's veterancy values increased, would be nerfed, and those who usually gain from vet, would be buffed.
This is what happened:
1. T2/T3 is made riskier, because these units increase enemy vet more than before.
2. Larger units that can gain vet, like ACUs and Experimentals, now gain vet much more quickly when fighting T2 or T3 units (and already gained very quickly when fighting T1).
So the new veterancy has buffed experimentals, which were plenty strong already, and nerfed T2-T3 units, which were underpowered.