Arnuz: I suspect the idea is to get to max size with housing then who cares about the rushing loss. While housing the prod malus disappears. And to build low level troops, that don't need the max prod anyway
Not saying that I like goblins mind you ;)
Population isn't usually the big limiter on rushing production. Gold is.
Building housing each turn in a goblin town (population growth racial) with the Expander skill will get a Village to size Town in 6 turns, and a Town to a City in 7 turns. That's 13 turns of the town doing nothing but building housing to go from Village to City, which also means it is making a little less money than a town building Merchandise. It takes 9 and 11 turns to go Village -> Town and Town -> City if you don't build housing. For reference, we stopped Arvandos at Turn 24, and the outcome was already decided several turns before then.
A goblin City under Mab with no extra buildings will generate 25 hammers per turn. This means 4 turns to build a Builder's Hall unless you pay additional gold. A Human
Village under someone without Technophobe produces 30 hammers per turn and can build a Builder's Hall in 3 turns without rushing.
Adding the first two Production buildings to Mab's Goblin City brings the city up to 45 hammers per turn. This means the city needs two turns to build an 80 gold Butcher (a T2 unit) or it can do it in one turn for 150 gold. A T3 Goblin Troll costs 140 gold at base cost. A 55 gold T2 Wolf Rider can be built in one turn if Mab spends 75 gold.
By comparison, a Goblin city with two production buildings but NOT Technophobe generates 60 hammers per turn, which is enough to output a Wolf Rider every turn for no extra cost, or produce a Butcher in one turn for 120 gold. Add Constructor (which Technophobe blocks) and the Goblin City can produce a Butcher in 1 turn for only 90 total gold.
A Human
Village with the first two production buildings can produce a 60 gold T2 Cavalry in 2 turns, or in 1 turn by paying an extra 20 gold (total 80 gold). Bump that Village up to a Town and the Cavalry comes out in 1 turn for no extra cost.
Technophobe is
brutal to your economy.
Edit: While building Merchandise, a goblin village with full farms generates ~53 gold per turn. A goblin city generates ~77 gold per turn.