A long while ago a strong defense meant your troops had a chance of absolutely no damage then Inno said a hit would do a minimum if a tic of damage. If a spearfighter hits your hover tank at least one tic of damaged happened. Keen eye doubles that damage. It does not matter if your defense is 2200. If a hit happens and keen eye procs (It does more than 1/3 of the time in JM) 2 tics of damage occurs. This is an outcome Inno wants. No damage means no chance of diamonds being used... My defense is awesome but I switch out damaged troops every 4-5 fights. I understand fighting...Lecturing me destroys your message. But then again most of what you put does too... Most online games use what casinos use to work players to spend real money. Guaranteed damage is one example.
Mostly the "lecturing" part was a reflection of the condescending tone you brought into the thread directed at me mirrored back to you.
Needing to switch out troops every 4-5 fights is hardly something to gripe about. If anything it means the fighting is *still too easy*. 2 ticks of damage taken is peanuts. You still make hundreds of troops a day, have tens of thousands in reserve, and sometimes might do thousands of battles in a single day. This is not exactly compelling gameplay.
As for adding the minimum 1 damage tick, that happened way back in tomorrow era. The rationale for it then was not some conspiracy to make players swap troops more frequently. It was to combat the possibility of a fight without resolution owing to the new microwave blaster which could theoretically lower an enemy unit's attack to 0. If you had them on both sides there was the possibility for neither side to do any damage to each other at the end of the battle. Hence, minimum 1 damage and the battle is sure to have an end. There were other solutions like setting a round limit and then declaring the defender victor. But back then minimum 1 damage wasn't something much of anyone worried about. Noone was seeing that apart from some imbalanced hoods with spears attacking tanks and towns with way too many watchfires (where 1 damage a hit generally isn't enough to win anyways - and you don't have to heal defenders).
Equally I'm sure Keen Eye was added because it was an interesting ability (Mars came out before GBG) - not some great foresight that people would be grinding 1000+ fights a day and if you do 2 damage instead of 1 to them it somehow encourages them to spend more diamonds (the only place I spend diamonds on healing units ever is in ages where I'm relying on unattached above-era units). We are not playing GBG the way they intended it to be.
Keen Eye was first increased in SAAB because of player complaints that the units weren't "better enough" than mars units. They were going to hold it steady.
Keen Eye has not been replaced because they're lazy and are copy-pasting everything they can from era to era and would need to come up with something genuinely new to not have people using past-age units because they have keen eye and the new units don't.