Some characters may seem to be weak at first but as you go along, their abilities could increase which could help in strengthening your team. Upgrade the basic skills because they would be useful in your battles too. In looking for shards, you might want to consider joining the Squad Cantina Battle and completing hard mode battles. Also, check areas for shipment tabs since they might have shard packs.
To give you a better understanding of the game, here are some of the best leaders and things you should know about them.
1. Barriss Offee (healer)
He can be considered the best healer in the game. She could heal a lot of injured team members all at once and she has the ability to heal passively as the party strikes enemies. So far, shards for her have only been found in bronzium data cards.
2. Clone Wars Chewbacca (tank)
At first, this character may seem weak but it could be handy in acting as a tank and taing away fire from party members that are about to die. He is not that effective in attacking but he serves as a good target to allow the weaker ones to live longer.
3. Jedi Consular (healer)
He is another good healer which could heal an entire party. He is good as a starter unit and throughout your games perhaps. With his lightsaber, strong attacks, and group healing, nothing could go wrong.
4. Obi-Wan Kenobi (tank)
He could stop enemies’ abilities and may even remove turn meters. With his increased evasion and raising of everyone’s critical chance and evasion when he dies, he is indeed a winning addition to your team. Obi-Wan requires a lot of resources to unlock so use the Star Wars Galaxy of Heroes credits and shards hack to get more if you need them.
5. Luminara Unduli (attacker)
Another group healer but with strong attacks. He has a force blast which has the ability to stip the skills of your enemies for a certain period of time.
6. Count Dooku (support)
He has the ability to strike twice in a row. His meter recharge is fast and his counter attack rate is at 100% which migh cause DPS hogging. When he is out there in battle, healers may have a hard time doing their jobs so it’s best to eliminate him immediately.
7. Darth Vader (attacker)
When it comes to the dark side, he is very powerful. Attacks also cause damage that is good enough. When teamed up with other dark side characters, an increased group attack power is very possible and this could easily take down opponents. Shards for him has only been seen in Achievements so far.
8. Darth Maul (attacker)
He is good in dealing with consecutive damages. He could attack groups and for Siths, he has group evasion passive.
To get more list of characters eligible for leaders, check this database.