It is in Default Reach Playlists so you don't have to worry about it if you love playing those Playlists.
Sword Block is an annoyance for me. The Energy Sword was a weapon that was always meant to be feared and it is a Power Weapon. Don't get close to it. Sword Block makes that concept redundant and can give an unfair advantage to the victim and a severe disadvantage to the Sword Wielder.
I dislike the removal of Sword Block as well, however taking it away makes it more like past Halo multiplayers. The Sword is indeed a power weapon, so it makes sense that you can't block it; can you block a rocket? A shotgun shot? AL not included, however 9/10 times Sword Block didn't work to begin with.
It's frustrating when you get killed by it, however it's great when you're the one killing.