There was just as much Uhura in TSFS as Sulu & Chekov if you go by lines.
Sulu had the 'tiny' scene
Chekov the destruct scene and they are just background button pushers for the rest of the movie
I am a crazy line counter
I counted all the lines for the main regular characters in TSFS up till the stealing of the Enterprise, recently.
Uhura has about 30 lines
Sulu about 25
Chekov about 20 and
Kirk nearly 300 lines
and he's just getting warmed up, the others by that point had had their spotlight time.
Anybody who truly thinks that Nimoy changed balance of focus for the minor characters is just unaware.
In trek 3 & 4 he gave them each a little bit to do in one scene and they thought it was some kind of big deal.
TOS was the big 3, period.
Nimoy was just able to massage the egos of the other actors to keep them happy, not expand their roles.