I have SEE and the ult mats ready for him but I'm not spending them on him since I don't see the benefit to it.
Will I be able to beat SLKR or JMK? No.
Will I be able to beat Reys? Maybe but I don't face many in arena anyway.
Do I need it for TB? I dont think so.
Do I need it for AB? Maybe but with my current sith I dont think I can 3* the mission.
Will it improve dramatically my CRancor scores? IDK about that. We just beat it first time.
Rather save the mats for the next GL I get.
If I'm wrong in any of these let me know. I'd be happy to give SEE the ultimate if it helped me progress, especially in CRancor