I think it'll be necessary for large cities that are inhabited by people that need to eat a normal amount or else starve in some weeks. Goblins might not fall in that category. A human capital would likely only be supportable with farming, though I'd consider any real world counter-examples from the right period. What were the biggest fishing/hunting-fed settlements back then (that didn't also get a lot food from crops and livestock -- theirs or otherwise)? Does the answer change much if livestock is included but not crops?
Fishing can provide a lot, as long as it's done on a large-scale or in a particularly fertile region. Hunting, on the other hand, crashes available stocks very quickly. The Anasazi, for instance, completely predated the deer populations around them in twenty years. There are no settled communities with built structures that relied on hunting to fulfill a real food security need (as opposed to a customary or luxury one). Only through pastoralism can a large group maintain enough food security without crops, and even then they supplement their food security by harvesting the crops of nearby agricultural communities (through tribute or warfare, either eating the grain themselves or foddering their animals with it). Also, much of our agricultural ouput, today and in the past, was for feeding livestock, so a strictly carnivorous people could still raise wheat to fatten their cattle (or, if they had some kind of cultural desire to eat "wild" animals, to increase the local population). Livestock are also a mixed bag when it comes to diet, with ruminants more resilient than single-stomached herbivores like horses.
Granted, a fantasy world can provide more options, and if you had an annual Wyvern Flight when the Wyverns do the equivalent of migrating to Capistrano (or overland zombie whale migrations--with some method to reasonably cure zombie meat, of course) then you could foresee a system where a larger population could survive off of hunting because hunting has become more like fishing (very large stocks with comprehensible patterns that replenish regularly). Maybe goblins spend more of their time hunting underground, but even if that were the case, the DF underground would have to be thousands of times more teeming with life than the average hardwood forest.