Only Species 8472 have proven problematic for the Borg, all others are just awaiting the day of their assimilation...that is if the Collective deems them worthy--maybe the Borg assimilated a Voth and found them lacking in their pursuit for perfection.
Commander Austin Harris, First Officer, Deep Space Nine (by FltCpt. Bossco)
8.01 - Darkest Before Dawn
(Chapter 8 added, 12/09/2015)