So I made posts on WoW forums about this, but not much response (only 1 really), and I'd really like to get some opinions on it, so here you go.
I'm quite excited for 5.2 to come out, with a new raid that's apparently on the scale of Ulduar. I'm wondering whether the amount of bosses in one place is truly what makes a raid "epic". I feel a lot of the best raids were epic in a sense that they were not linear. You could choose where you wanted to go next, which boss to fight, and it'll all still end up leading to the final boss. Bosses being optional might not be a good idea, as eventually no one will just do them (Ignis, Razorscale etc you get the idea, although it was due to them having no hardmodes really lol). I didn't really enjoy the cata raids so much partially because all they really were were just straight lines, you can't travel in two directions, you have to go in one direction. You can argue in DS you had the choice of going Zon'ozz or Yor'sahj, but please, that was like a short flight followed by a 5 min boss fight back to a straight line again. Firelands was different, so why did people hate it so much? Not too sure tbh, I liked it, but I'm guessing the constant red and black just bored everyone to death (#bleak). That's just my problem with this model, there's basically no choice at all, and looking at the maps of the new raid, it seems like it's going in this path.
In conjunction with that, you have to consider the size of instances as well. Looking back on it, raids have become a lot smaller since Cata hit, with MoP raids included (although ICC wasn't really too big, but the 3 wings gave it a better feel). You can argue that the number of bosses contributes to this, but when you look back at SSC and TK, they only had 6 and 4 bosses respectively, yet they were huge (at least SSC was). I feel this bit contributes a lot to how epic a raid is.
To be honest though, even looking back at a lot of old raids which were deemed "epic", such as BWL and Kara, they were pretty linear too, but I just didn't get that feel. There's probably some other factor out there I'm not considering. That being said, tier 14 has been highly enjoyable and I feel boss fights are really top notch right now. Although heroic mode still doesn't change strats and gameplay (lol all of DS) much for a lot of bosses (bar a few like emperor, sha, vizier, spirit kings, etc), it's changing a lot more than any tier since Ulduar where it first started off. Can't wait for Throne of Thunder.
Edit: Everyone has their own definitions of epic, and I accept that. Just trying to get a general idea from people here.