Hello @felker_s
Palp is by far not weak (at least in GA he is very strong). You should try to always stay on the move. Jump high and dodge twice and then jump high and repeat. While in the air you can shoot lightning at your opponents. Be sure to press both left and right mouse (if you are on PC. I don't know the combination for the consoles) to shoot lightning from his left and right hands. 
Palp is able to multitask, so you can use his chain lightning and both hands lightning at the exact same time, capable of one-shotting every single trooper (except for enforcers). The animation for the stun lightning takes too long in my opinion, so never use that if you are under fire. Only use it if you catch the other heroes off guard.
The middle ability (dark auro) can be used to your advantage if you activate it while going towards enemies, but don't use it while in a fight.
Palpatine is by far one of the strongest heroes in the game, capable of incredible manoeuvrability, complete health regen without making any kills (with a certain star card) and very high damage output. Once you master him, you are unstoppable.