In the last album I was also fighting with sibilances in vocal tracks. I tried dozens of settings with 6 different deesser plugins (BT DeEsser DS2S, TB_DeEsser, SleepyTime Lisp, TB_Sibalance, VX-64 Vocal Strip, Tonmann DeEsser). In the end I was not really satisfied, but ran with Lisp (the best IMO). Beforehand I tried to reduce the esses with Melodyne.
I have identified 3 problems:
1.) When I had a perfect deesser setting for one case, it was rather bad for another in the same track. To change the settings for each case (automation) was too labor intensive, I thought.
2.) After a while Working on one track I could not hear anymore if the reduction was too much or not enough.
3.) Reducing the ess-sounds beforehand (Melodyne) did not include problems caused by later compression or other modulation.
Thus I am still waiting for the "wonder" DeEsser plugin
(I have already considered some).
Marc