Are Nephenee and Soren not that good

So I've played through Path of Radiance and Radiant Dawn quite a few times over the years and Soren and Nephenee have always been two of my best units(like I only remember them dying maybe twice in all of the times I played through before now) and I didn't really invest in them. Since last year I did three play throughs and they were never very good so I talked to my friend about it and he said that they're usually not that good if you don't invest in them and he always wondered why I'd been so lucky with them. Did everyone have his experience with them?