Did they raise city defense in a patch or something?
Rocket. Battery.
At +18 strength (+23 with quest added), it's quite a combat strength boost to cities early on. Then the Defense Perimeter adds another 10 strength plus a heap of HP. Also, tech modifiers and population modifiers remain the same between BE and BNW, but base city strength is 20 in BE and only 8 in BNW.
Here's some more comparisons for a clearer picture:
Marine: 14 + 2 attack (if chosen) = 16
Swordsman: 14
Brawler: 24 + 10 if alone = 34
Musketman: 24
Rifleman: 34
Artillery: 20 + 2 city attack + 6 city attack (if chosen) = 28
Catapult: 8 + 16 city attack = 24
Gunner: 14
Composite Bowman: 11
Crossbowman: 18
Rocket Battery: 125 p / +18 s (+23 s*) / +15 hp
Walls: 75 p / +5 s / +50 hp
Defense Perimeter: 150 p / +10 s / +40 hp (+50 hp*)
Castle: 160 p / +7 s / +25 hp
Both defense buildings added together:
BE: +33s* +65 hp*
BNW: +12s* +75 hp*
(Also, Walls[5] + Castle[7] + Arsenal[9] + Military Base[12] = 33 = Rocket Battery[23*] + Defense Perimeter[10]
)
As said, with the both of these buildings available fairly early, it's like having walls and castles up -- actually, it's even better than that.
So, you were attacking walls and castles that have a much higher strength (in BE) with Musketmen (Riflemen*), catapults, and something a little better than composite bowmen.