I did a quick search on this bug, but either it hasn’t been addressed or my search-skills are far behind. If I did make a duplicate, feel free to remove/merge.
The signet has been buffed back in the March patch if I remember correctly.
The signet’s passive (+10 plus one per lvl precision) has been doubled. On level 80 the signet has been buffed from +90 precision to +180 precision. The tooltip however still says the original “10 plus one per lvl”.
Video link
Server: Whiteside Ridge
Race: Asura
Profession: Thief
Level: 80 ( happens while scaling as well)
Should be an easy fix.