Well, if everything available at end-game can be completed by groups where "a large chunk of the players really don't know how to use all these skills to their advantage" I'll be VERY dissapointed. The Erebor raids might lack imagination or depth on t2c, but at least 2/3 are a challenge. Skraiding and the vast majority of scaled instances are complete garbage for anyone in the instance who cares about more than the loot, or simply socializing.
Obviously a lot of things could be different with class revamps, but if these instances can be completed when the healer you brought is level 10 and has 1 healing skill, why bother with an instance at all? And if they can't be completed with a lvl 10 healer, why let lvl 10s in in the first place? Hopefully the class revamps take care of this issue.
Skirmishes have optional encounters too...
It is true that to allow level 10s in and for them to have a fun and satisfying experience and want to play more that success in a Big Battle won't be an overly difficult thing to achieve.
It won't be all that hard to 'win'.
That's why we're introducing the medal system. What we're doing is basically grading you and your group every time you play the space. Each action you take, or don't take, thing you defend or don't, objective you succeed at or fail will add or remove points from your score. I would expect most level 10s, on their own without having many Promotions, to get a grade of D, a bronze medal. Enough to pass and get some measure of reward but not really anything to brag about. While the top end level 95 players who are kitted out and have a lot of Promotions are pushing the boundaries and attempting to get As, platinum medals and the best rewards the system has to offer.
It's not just that you're still standing then when the wall blows up. It's how many Rohirrim are still standing with you, how many banners and flags of Rohan still fly, how many injured soldiers were you able to protect, how long did it take to dam up the culvert and how many workers were lost doing it, did your catapults survive the battle, how many pieces are the gatehouse doors in, how many supplies did the enemy burn, etc etc etc. Each of those events and more contribute to your overall grade in any given Big Battle. Being able to coordinate and communicate effectively handling them all across a battlefield while your group is spread out and working on separate parts and pieces to the same overall problem and goal we believe will create a large degree of challenge.