Shaak ti mass cleanse Stunning Rex only for a cleanse to come is painful. also as mentioned her unique gives the clones retribution and she can heal.
Using a traya team with thrawn is your best bet as mentioned above, but that removes easy counter for bugs.
I'm currently running a clone team in arena sitting around my top 100 2015 shard ,and I can say that when shaak ti dies first it's a harder battle.
Back to the topic if the zeta on tactical awareness is a must and I can safely say yes IMHO