I think the 2x zeta investment in Shaak ti is well worth it. My Shaak ti clone team can hold it's own against some G13 DR squads and most other top squads like grievous, csl, etc..Honestly I don't think GAS leader ability is all that great for a clone team. It only really benefits him, whereas Shaak tis is a huge boost to damage and survivability to the entire team. I also don't think GAS has much real synergy with clones (even the 501st ones) other than making them invincible until hes killed...or retreating (which isnt all that hard to do). For example arc troopers turret attacks when arc attacks out of turn, but GAS doesn't really facilitate that where's Shaak ti gives all clones retribution. Idk just my 2cents. I think shes worth the investment