That's about what I'm seeing with my 3TB. Really, the Fusion is a nice compromise of price, performance, and capacity.
Write speeds, though not as fast as the new SSDs, are still screaming! And most of us would be really hard pressed to find something that'll read that fats, so writes wouldn't be the bottleneck. The important element is how much the very minor performance difference will impact your life. After three years with a Fusion 3TB, and with loads of other SSDs, I say not much at all.
I think most of the people out there complaint about Fusion drives have never owned one. After almost three years with a FD, I ordered one again with my new 5k. And I love it!
Congrats on the new system!!!