Tauroneo has not only bad availibility, but also he will outclassed by Gatrie. FE10 Gatrie is probably the best armor knight / general in the entire series (60% speed growth). However I don't see a point to bring generals / marshalls to the endgame. Their caps aren't too great. Jill and Haar are better options.
Elincia is overleveled in part 2 with crappy stats for a tier 3 unit. Even one tier below Marcia with PoR-boostes has pretty much the same base stats as her. In part 4 Elincia's stats are behind the other units. So I recommend to give her paragon. Her strength and speed growth are great, has an unbreakable brave (silver)sword and is a flying healer. So definitive endgame-material.