I completed Into the Mountains with Lini, Seoni, Amiri, Meresiel,and Harsk with Seoni dying, and it did not give me my role card with Meresiel or Seoni. It just showed

Dead characters does not get scenario rewards. That Merciel part is the strange one. If you go to character info, does it show the scenario completed or not to those two characters? (Completed tab)

Yes, check your two chars completed every scenario in that adventure, it doesn't count the last mission. Then complete what you miss and you ll get the end adventure reward at that moment.

I looked and discovered that Meresiel did not complete Them Ogres Ain't Right.