After a bit more experience with LOTRO skirmish soldiers, I've seen an interesting design issue with the system.
Depth, As In Variety Of Options
Almazar has a writeup of the soldier roles, which was further discussed on this week's LOTRO Reporter. His critique of the Archer class seemed a bit familiar at first - I'll concede that, with all the NPC's that are running around your average skirmish, it can be hard to even notice the added DPS from your soldier making one individual foe die faster.
That said, the thing I really noticed about the Archer was that they actually make a half-decent off-tank. Archers come with medium armor, and I further toughened mine up with a trait that bulks up their armor and an in-combat morale regen trait. The Archer does entirely single-target attacks, so they're not going to get more than one foe the way the squishier Sage soldier will. With the survival enhancements and decent single target DPS, the Archer can comfortably solo the single weak or regular solo mob that they decide to attack, without my intervention.
I don't always want them to do this, since my goal is generally to gather all the foes up for AOE, but it can be useful in certain defensive skirmishes when you're running around trying to trigger some encounter for bonus skirmish marks and want to take a little bit of pressure off of the friendly NPC's. I could also see caster classes with skills that can be interrupted by damage happy to have one foe out of their hair, without attempting to micromanage the tanking soldier (though I suspect that the tank would still be superior for those classes). It's still not my favorite soldier, but I was impressed with this little chunk of versatility.
But limited depth, as in further development?
As Zubon noted skirmish soldier training seems to hit a "soft cap" of diminishing returns very quickly. I'd argue that the increase in soldier power, especially considering the increasing cost in skirmish marks, starts to trail off to the point of irrelevance as early as ranks 6-7 (before which the soldier is almost useless in some cases). It feels like they decided how effective a fully maxxed out soldier should be at rank 20 of everything, but then decided that the early ranks needed to be more rewarding and ran out of room to reward the higher levels.
There might be several reasons for this. Many players will want to try more than one soldier type, either for experimentation (as Almazar and I both did) or because the soldier you want in group skirmishes is different from your favorite soldier solo. There's also the quirk that the system is designed scaling from level 30, but many players are picking it up as late as the early 60's because it was only implemented in the new expansion. Something had to be done to help existing characters catch up more quickly than would be possible if the soldier advancement curve went more smoothly.
As an aside, I find the concept of doling out 90% of the overall power level at something like a third of the soldier level cap interesting. Would this work for player characters? My feeling of lack of progression with the soldier argues otherwise. Then again, this type of system would largely solve some of the issues with vertical progression and attempting to play with friends of different levels. Who knows?