It all depend on mode you are using her.
For example in GW def empower looks good cause she is procing more quickly, and making bigger threat, but on other hand it may be easier to kill her with AC od damage reflect skill.
For raids empower is good option imo, just as for Arena as it helps to quickly hit opponents, and on Arena rarely you will get max proc speed (but it depends if you are using PD or not)
For Lava empower will not be good, since she will quickly reach max attack speed, and empower will be useless. SD would be better in this situation.
I keep Empower on mine for Raids, but during Lava time i need to change for SD for additional damage, just in case. Overall i think empower is good crest/insignia, just you need good def talent, or Revive not to loose GS in that process.