ZoS unconjugate all stuns from spammables (Dizzy, frags, deep fissure, clench etc.). But they added stone giant, stunning spamable. It is balanced because you have to cast it 3 times. That is fair imo.
If dizzy swing can consume off balance to stun, it will be weaker than old one but it still can stun.
-Enemy will have more time to react if you cast 2 swings.
-You will be rewarded more if you proc off balance from another source, the reward is OPness of old dizzy swing. Enemy will have time to react because they see themself off balanced. So it is still not OP.
This will reward high skill and keep game more balanced.