Note: I'm not sure if this is caused by Yareli's Merulina or Yareli's Aquablades, or a combination of both. Merulina has other bugs, so I think it might be that.
While running Sanctuary Onslaught, using Aquablades while on Merulina causes the Efficiency to not go up. I have not tested either one by themselves enough to see if one or the other is causing it.
I was using Surging Blades augment while testing this.