The reason I don't consider this a nerf to anyone, is that I've been playing 1 grenade in the assault the entire time.
I've also seen on a lot of forums how "all models getting [insert special grenade] is stupid and useless now" Ignoring my above statement that I think it's been that way all of 7th edition: It's still nice to have more than one model that can plant the melta bomb or toss the krak grenade. I'd rather throw 1 haywire grenade or plant one melta bomb as long as something is alive in the unit, rather than have to protect the ball carrier. Of course points are a consideration, but just throwing that counter point at it.
You might not consider it a nerf, but I, and a huge amount of players who relied on meta bombs to take down tough targets like knights certainly do.
Orks had to sacrifice 3 attacks on the charge for one single meta bomb each, under the meta bomb rules it is an attack per model, and that seemed fair and reasonable for a specialised unit like the bustas. There is no ranged profile for a melta bomb, its a bomb not a grenade, itll never be thrown but now it's been lumped in with krak grenade abuse, it's how I always played it, how everyone in my local club and store played it, and how it was played at the tournaments I attended.
It's not like it was an easy thing to do, to maneuver a 5-10 man unit across the battlefield in a flimsy truck, leap out and successfully assault a Knight. Pulling that off meant you deserved to take that knight to the ground.