If you've ever wiped for a lot of times in a row on the same boss trying to implement a strategy that you knew as correct, you'll know that this can quickly get boring. There is no element of surprise, no adapting to circumstances, you simply need to perform just as the battle plan demands and everyone else needs to do the same.
For me, this is a core issue with raiding. I don't play MMOs to prove that I still have the same amount of twitch as an 18 year old (I don't,) I play the because I like to make meaningful decisions. I believe, however, that the problem doesn't simply lie in encounter design. Sure, WoW's boss fights are very scripted, but even if you go into less scripted environments like PvP you get to observe some of the same problems. The issue is rather that coordinating 25 or even 10 players in real time while also playing the game yourself doesn't allow for very complex decisions.
Your run-of-the-mill raid leader determines the battle plan beforehand and then is limited to calling out warnings and maybe making one or two adjustments on the fly. Her main focus will always have to be on pressing the right buttons to play her character and to not stand in fires. If fights were less predictable and more complicated it would simply be impossible for the raid to adopt new tactics in time. Sure, single players can react to a changed situations and the raid leader can try to give commands - but coordinated group responses are almost impossible.
I'm not a big fan of the military myself, but I do have a certain interest in military command structures. In the real world, battle plans are made, but rarely survive the first contact with the enemy. Detailed command structures make the adaptation to new circumstances far easier, and no one would expect the people who decide on high strategy to fight in the front lines at the same time. You might have a sergeant or corporal relaying orders and coordinating small subgroups there, but the higher command will focus on coordinating them instead of hand-to-hand fighting.
"No plan of operations extends with certainty beyond the first encounter with the enemy's main strength."
I think that an MMO that allowed for such a tiered command structure, complete with fitting UIs for the different ranks, would be much more engaging than anything we've seen so far in that sector. Sergeants would be able to see the status and positions of their soldiers as well as a tactical overlay of their orders. Higher ranking officers would get strategic maps of unit positioning and issue commands through those with appropriate voice-over-ip options to communicate with their subordinates separately. Depending on the scope of the game there could be another higher level of command dealing with the large-scale deployment of armies.
Savage 2 implements one of these features, but I didn't much like the implementation when I played it. The battles were too small-scale and the RTS and action components didn't really mash all that well. Still I think that the concept has a lot of potential and could make for some very cool actual realm vs realm play in MMOs as well as allowing developers to take the leash off of raid bosses. Learning a boss's script through repeated dying really isn't very immersing or fun.