They are big, scary, rather rare in the nether, and make scary noises. Yet they are one of the easiest mobs in the game. There fireballs are so weak they cant even destroy stone. 1-2 arrows can kill them, and they are big, so it is easy to hit them. There fireballs go above you. There fireballs move very slowly, so it is easy to hit them back. They are easy to dodge because you have awhile to react, the ghast fireing the fireball makes a noise right when it shoots it, and they shoot from far away. And again, if you are about to get hit, you can just hit it back... And they won't shoot again until that fireball blows up.
So you want them to shoot mini-nukes? That would be the effect of the fireballs on the nether if it was buffed
Also, it's not "that" easy to knock back the fireballs, specially when they are far
Also, it's not "that" easy to knock back the fireballs, specially when they are far