I did some very minor testing at level 50 Lancer on level 50 Amaljaa Drubbers at the beast-man stronghold.
Used only autoattack. Killed about 20 mobs with 350 accuracy, then killed about 15 mobs with 365 accuracy (3 +5 acc rings.) My accuracy didn't seem to go up according to a parser. Of course my test isn't super accurate because of the low sample of mobs, but most likely, accuracy is capped at certain levels. Any time they used acc down, I turned and stopped fighting until the debuff wore off me.
Was wanting to know if anyone did any tests on higher level mobs, or did any testing on weapon skill accuracy.