ACK! get zetas in ship shipments. Get Rex/Maul in guild shipments.
Given the speeds you mentioned... I would say keep vader:).
Yoda gains 10 Speed in his gear 7 set.
Yoda gains Speed no speed in his gear 8 or 9 sets
Yoda gains +6 speed in his gear 10 set,
Note: gear 10 set is the gear available at gear 10, to promote to gear 11.
So if you get Yoda to gear 7 and add the gear 7 gear that gives speed thats enough.
Equip the best speed mods you can to Yoda, I have mine at 265 speed. 230 should be very doable.
The idea is for Yoda to go early before he can be debuffed or killed.
You can try to use REX, again the key is him surviving to remove the Debuffs. It will be a nice counter push if you can use his special (removes debuffs, adds tm / tendacity up).