The best replacement for fluency is accuracy.

The best alternatives to fluency are rated as following:
★★★★★  accuracy
★★★  comprehension
★★★  proficiency
★  accuracy esl
★  automaticity
★  fluidity
★  fluent
★  cognitive efficiency
  decoding
  prosody
  accuracy english
  reading accuracy
  reading comprehension
  vocabulary
  accuracy language
  literacy

Your alternative for fluency is not listed? Suggest!
Speaking about fluency, one probably shouldn't forget about comprehension.

Other search terms related to fluency and their ratings are:
★★★★★ comprehension
★★★ repeated reading
reading
You have in mind a companion for fluency and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of fluency in all years. Click on graph for more.
fluency
accuracy
comprehension