However, I want to collect my best units and level them up before reaching Undelwalt (The fallen is one of the reasons). I stick with Jorgen Warrior. I just have to find one left item, sword of remembrance, in the aqueduct, and he dualwield KAtana. I don't know if this is true, but there is no other leader dualwield Katana. And i hope I can make him a ninja.
Uhhh... Jorgen Sage =/= Regular Sage. So no, Jorgen Sage does not get Immune to crit. And even if he did, it's not like it's a great ability, since AFAIK it only applies to him.
Personally, I'd go with Adventurer, since at least you can get him early enough to train him in Remedies if you so need another Remedy healer.
Aristocrat has the rare ward skill if you need another one.
Raider on the otherhand provides the best endgame usefulness, considering he gets Hawkarang and can provide healing if you train him a bit in remedies. --- Turn 1: Enhance Spells Turn 2: Overdrive, Water Blast X5