When it comes to WHFB Orcs and Goblins, regular old Goblins are the middle child. The one who always claimed "Mom liked you best!" of the other units in the army.
They have no Night Goblin trickery, like netters or fanatics. They have no squig herds or squig mounts. They don't hate Dwarfs.
They have no poisoned mounts or wall-walking, like forest goblins.
They have no T4, tusker charge boar mounts and chariots, no choppas, no warpaint ward saves and no super-armed shock troops like Orcs do.
They are just.... goblins. The basic troop model doesn't even have the option for a hand weapon on the sprue, so you have to convert them to get the 6+ ward save in cc. Sure they have wolves and wolf chariots, but they are completely mundane. They have war machines, but these are the basic ones from the rulebook (except for the Doom Diver of course.) What role do goblins actually fill in an O&G army? What are they good at that there aren't already multiple options for?
Let's take Skaven as our comparison, another horde army. Skaven basic troops are clanrats, skavenslaves, stormvermin. I'll leave off giant rats and night runners, since they are quite a bit different. The three troops I mentioned each have their specific rules and strengths. Slaves are amazingly cheap, pop when they break from combat, and you can shoot at an enemy in combat with them. Clanrats are basic and fairly cheap but you can attach a weapon team to them, or hide an assassin in them. Stormvermin are very similar to clanrats except they have better gear, a better initiative and weapon skill, can take a magic banner, and a unit of them can be boosted with a special character. Each unit has something special about them, something that can make them more useful. Goblins do not. They have hand weapons, spears or short bows. They might have shields. They might have command. That's it.
I have to admit, I have a thing for armies that don't include their best basic units. My Witch-Hunters army includes no Sororitas at all, and I'm building an army of all mounted goblins and discovering that there are exactly zero surprises in the army except for the die-rolls. Even the wolf riders and chariots don't have very much killing power, and now you need minimum 10 riders alive at the end of combat just to disrupt, so forget MSU gangs. Maybe the next army book will make their place in the O&G army more defined.
So here's my petition to GW: please give goblins something night goblins do not have, other than just light armor. Maybe a unit upgrade of a goblin big boss (as opposed to the current "boss" unit champion) that doesn't count against the hero points (perhaps with a lowered magic item point limit too.) Something. Anything. Please.