Dunno, Jagens recently don't tend to die off early but rather be permanent benchwarmers in your barracks.
Struggling to think of who takes that role more recently. In PoR/RD it was Titania, but she’s relevant all the way through. I tend to look to the beast kings in RD as the units that are very powerful and best to leave on the bench (although I usually just leave the Laguz on the bench as they can’t use the relic weapons later on anyway).
In Awakening, who takes that role?
In Fates, I guess you’ve got Gunter as a Great Knight in that role, although I always forget him precisely because I left him on the bench a lot- he soaks up hits but I also found he felt comparatively weak very quickly compared to, say, Seth or Titania. I guess you’ve also got Xander/Ryoma but the latter feels different due to being a swordmaster with all the vulnerabilities of lower armour if the enemy does keep targeting him.
In Three Houses, you don’t really have them either. Almost feels nostalgic to see such a character in the early game again, or at least one that seems designed to be considerably older than the others at the very start of the game, but that might be because I find Gunter so hard to remember, even though I liked his lines as Corrin’s weary retainer!
Reminds me of when I first played FE games and had no idea I shouldn’t be letting Jagen and Seth do all the fighting so that the young lord can power up instead