Shaak Ti lead is totally fine on offense and honestly in a few months I surmise we might get a few more clones to round out her squad even with General Skywalker taking all the 501st.
In the meantime, it's all going to depend on your roster. I would argue that you should prioritize getting Arc Trooper because the extra 501st means Rex gives everyone another 4% speed. If you want to use either Sarge or Cody for whatever your reason is that's fine too.
So I'll assume you're going Shaak Ti, Rex, Fives, Echo, and a fifth clone. Fives' revive zeta is the most important, then it gets a bit more questionable. I like Shaak Ti's zetas more than most, so I go with those two but Rex's is important too. Next is Fives' zeta to give him TM, then Echo (and yes it is worth it... any time you face someone with foresight , they will be taking good damage from Echo).
Arc Trooper's zeta is actually pretty solid in this team too because you can call him to assist a bunch and he will be counter attacking more with the zeta. In a General Skywalker team it really doesn't get used much at all, so kinda disappointing there.
As for modding, you want Rex crazy fast with some potency, Echo for crit damage and offense, Shaak Ti I went speed and tenacity though you could argue she already goes a lot since she gains TM from being damaged so speed isn't too vital but I want her going non-stop. With Fives i have played around quite a bit with mods. For raids, i go crazy high offense and decent speed since those stats get pushed to the 501st. If you go with a defensive build go crazy on health and protection since those stats go to the others. Added defense is nice, but he gains a boatload of defense when he has taunt anyway and he doesn't share that stat with the others.
Arc Trooper needs offense since that's all his turret cares about, Sarge needs crit damage, and Cody can go crit damage or offense.