Dawn I had nothing to compare to.
Well that's because she was introduced after the switch.
I think the only voice that didn't change was Gary. The narrator apparently did change for 2 seasons and then went back to the original one during the switch, that's why it doesn't seem different to you.
And the switch was really unnecessary, the VAs are still New York based, and some of them even return later on to voice other characters. For instance the person who voiced Misty went back to voice Maylene even after Misty got a different voice.
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Oh brilliant blade of cold as steel, rend the infinite darkness and crush my enemies to nothing... SAVAGE WOLF FURY