Not everything us essential, but specific ones are for specific content.
I quite like the idea of different loadouts for different content.
Like I don't need Low Blow when raiding. I do need Intervention for o3s. Shirk is great for o2s a different o4s, while useless to me in o1s and o3s. If I'm maim tanking o3s I'll take Awareness - which is also great for mass pulls in dungeons.

So again, there's no real issue having many useful skills when only so many are needed at once.