Terrorhuz is right that Chrono was fine before the nerfs (certainly not overpowered), and some forum frogs contibuted to worsening the class by complaining about not being able to dodge moa.
However it's not true that core power mesmer is better than chrono power mesmer, chrono has a lot of advantages like movement speed, lower cooldowns on everything, double elite sills, superspeed shatters.
The proper way to buff power mesmer would thus be to buff core power mesmer, and nerf Mirage slightly to compensate. This would help core, it would help chrono and it would help virtuoso - the three underperformers.