A redoubt buff won't stop Brits with APCs, the composition usually involves paratroopers too, and paratroopers have a ton of hp to tank any building but anti-tank towers. The Brits play the number game when it comes to the units that are going to be absorbing most of the damage from defenses, it's why they barely even need to use tanks: they've already got a plethora of ways to pull aggro off of their ranged infantry.
I had an interesting idea the other day: what if the british ranged infantry lost their +1 range for a duration if they get damaged?
I dont think british need a nerf. They just need to make other nations compete with british.
For instance, Japan is supposed to be a defensive nation.
The TC shooting invaders is a joke once you get higher up in ages.
Instead how about:
Stables/Garrison/Bunkers spawn 30% faster and spawn 1 additional troop than normal. + Disabling effects are 25% less effective against spawning buildings. Traps 1% more effective per age.
Chinese:
+3 citizens and +2 merc capacity instead of just 1. Mercs do 20% more damage and have 20% more hp and 2 Free random mercs per day.
Germans:
While under rally effect, troops take 50% less damage. Troop Damage +2.5% per age.
French:
-50% training time for troops and tactics. -15% troop cost. +1 troop Alliance gate space per age. -5% troop/tactic upgrade cost in Armory.
Greeks:
2% discount upgrade cost per age and 2% build time reduction per age. Increase the instant finish time to initial 30 min + 30min per age.
Koreans:
Resource buildings +50% health, war tactics +4 capacity(with the recent changes this makes more sense) 20% food/gold refunded and 35% oil refunded after being attacked. War tactics train 20% faster, tactics blessing 50% better.
Romans:
Army size +3% per age, mercs +2 slots, coalition troop size +15%, +3 troops for alliance gate.
I didnt put a ton of thought into the above suggestions, just an example of some things that could make other nations much more appealing.