It is pity that OP have no idea of raiding, at least in tbc.
About class stack:
Most of the decent guild have at least one enhance, two ele, one resto, sometimes even two resto
So in a raid there is often consist of 5 shaman, or op dont even know about that?
If you want to have the “no certain class or spec must be needed in raid” thing, please go to Wotlk server.
About difficulty of Brutallus:
There is only 3 reason that you can kill boss, especially for Brutallus:
1. You are much skillful player in PVE, which you minmax your own class and spec
2. You have all people with BIS before killing the boss, which is overgearing the boss
3. You use the best raid comb possible to get the best outcome of dps
Panacea and Promise certainly is using a mix of 1 and 2 to kill the boss,
Murlock shop is using 4 glaives and get 3rd place in Brutallus, which is method 2.
These are all acceptable kill, and they did multiple attempt before successful kill.
Now OP just want to boss to tuned down to be just able to down without those?
So may be please tell me which guild you are at and let me laugh during your progression?