Don't listen to this. Zadar is definitely a viable leader. I finish first in my shard every day and crush the CLS meta. I run Zadar lead, DN, Thrawn, Kenobi and R2. Im probably the only person on my shard that runs it and I have for quite some time. I am certainly not F2P, and have good mods which maybe make this more viable than a FTP but its definitely doable.
Go heavy protection on GK.. Make thrawn the fastest, fracture whoever (normally Zolo), Smoke screen to GK, Dots from Zadar (put him ahead of DN), DN steal, the rest goes from there.
Potency doesn't matter because almost everyone runs CLS lead now instead of Rex.
As someone above stated, SA works really well with Zadar lead to speed him up but for me to finish at the top there is no spot for him when fighting CLS leads as you have to have R2 in there for the smokescreen or you will get destroyed due to the AOE retaliation.