Like others said, this feature does take skill to use correctly. You need to time it right to the millisecond to perform it right. Besides, if they have a game type of or similar to infection in halo 4, sword blocking will be key. Was in reach, because I found I was one of the few able to use it properly, and also use it against the humans come the chance. If you do use it properly, it is a very good advantage for you in a gametype such as that.
However, I do believe that sword blocking in other game types are slightly unfair. For, I will use reach as an example again, if you work hard enough to get that sword, and if you work hard enough to close that gap, you should get the kill. Also, as mentioned, there is only one sword in the map, which spawns after a slightly lengthly duration of time. So, if you get it, you should have the ability to use it to it's full extent.
Why, you ask, is it any different from infection and alternate game types? Well, example, in infection, energy swords are far from scarce. Zombies all get to spawn with them. And when they die, they're right back in seconds anyway. So humans deserve that ability as a method of survival. Because unlike the zombies, humans do not go back to their original selves. Just think about those aspects.
-Bullet