I don't think Jedi need any anti sith abilities. Why? Because every toon not jedi is anti sith.
Sith have the lowest health in game (except savage, but umm yeah). While Jedi have the highest health (an average). Toons that can easily one shot sith, can't one shot most jedis.
Jedis also have healers, where sith do not (I know night sisters are dark force users, but not sith, and not sith in game)
This is important when looking at leader abilities. I know most are worthless, but most are ment for either Jedi, or sith, except the 2 big anti Jedi toons, sid and dooku.
This issue is only few toons are actually usable in current meta, and Jedi is the way to go right now. Giving them anti sith, while pretty much being anti everything not sith as they are now, would make everything outside Jedi worthless in the meta right now.