Ah ... it figures you kids kicked this off whilst I was off on vacation! Fin, Gravidy - you're not alone in enjoying BBs. Especially, for me, the Helm's Deep ones - still kinda get my head wrapped around the ones in Gondor. Rosie, I'm glad you were able to get into it; I'd be happy to help where and as able, too. Give me a shout on Discord; best opportunity to actually reach me, because I might be on any of 8 toons ... or none.
Anyway: I've run Helm's Dike with two a whole bunch - preferably an Engineer and a Captain (BB role, not the class, though that works as well) - and can be really smooth ... IF you take the time with an Engineer to set up the field before actually starting the battle (move/place barricades, set up siege weapons). It's probably my favorite of the bunch. Taking the time to set the field allows you to score really well most times you run, at least solo or duo. I've never run it on Fellowship; that would be a great exercise, I think, but I'd want someone who did it a few times leading.
Deeping Wall is not too bad, and you can usually score pretty well; I love the use of heavy siege weapons on that one :-D . But it throws some really tough side quests, and I've failed those a bunch. Those can also cost you with some of the basic scoring as well (thinking of keeping the flags intact, primarily). Again, I've never done this beyond the usual solo/duo; I can only image what craziness applies with a full raid (I'm told you have to protect the *entire* wall on that one).
Deeping Coomb I've found to be quite fun; again it pays to prep quick, setting and upgrading barricades on the two primary entry paths. From there, it's really about DPS, even on the side quests.
Fin, I absolutely agree, of the bunch Glittering really is the hardest. The wide and confusing separation of locations, especially when the side tasks hit, makes it rough. And it seems like one or two are almost impossible to complete with a good score (thinking particularly of the defilers and trolls attacking the passage to the camp).
Looking forward to seeing/hearing more on this ...