if the attacker gets 50% back and the deffers get 50% aswell after a week, the deffers will have much more def than the off guy. Deffers already have a rather big advantage at the moment with waterditch/wall/morale.
Let's take a concrete example:
(When I talk about troops I talk about their crop consumption not a single unit)
Two average players with 5 villages of 750/800 pop each.
Off player (teuton): He produces troops 24/7 on one village, with barrack and stable lvl20
infantry: 882*7 = 6174
cavalry: 216 tks, 648*7 = 4536
subtotal: 10710 crop consumption in a week
Considering he crashed a 20k hammers, he will get back 10k after a week, that's the same hammer after a week.
Def player (teuton aswell):
The def player that stopped the above said hammer lost 20k troops, after a week he will 10k troops back.
Now a good deffer will have 5 villages where he produces infantry on 3 villages and cavalry in the two remaining villages with barracks and stable lvl20:
infantry -> 569*3*7 = 11949
cavalry -> 266*2*2*7 = 7448
sub total = 19.397
total = sub total + saved troop = 19.397 + 10.000 = 29.397 which is 41.9% more than the off player.
So this obviously scales in favor of the deffer not the attacker week after week, so in the long run they will be able to def way more villages.
But I just realized that the survival feature wouldn't change the fact that def players are still op. they just produce troops way more quickly than an off player if they have a well set up account.
After thinking about it more deeply, the feature itself is pretty useless unless some new mechanics to really hurt the enemy are put in place. If everyweek we attack the enemy with the same hammer and that the damage is so irrelevant that they will have more troops than the attacker anyway the following week, this feature won't change anything on the current state of the fights except helping even more deffers.