Attackers don't have to hit blind.  Its true that a defender can change things after hamlet is spied, assuming they are paying attention and see battle report in time.  With boosts, attacker can cause an attack to hit almost immediately after spy report (if you get a fish that gives you lots of points and you don't want to risk it escaping).

It is also true that defenders can get mad about the same attackers harassing their holdings over and over and can set traps, especially when said attackers are very predictable.  I've trapped a couple who always hit with 100 dragons during the same time frame.  The fact that not all attackers are smart and that they can lose a lot of offense if they attack something bigger than they thought it was does not change the fact that the risk is much higher for defenders than for attackers.  

Defenders troops are exposed the whole time, open for anyone to attack, and I've seen some massive offense thrown at hamlets (one lvl 64 hit my hamlet with 18k dragons and 300 great western dragons...I'm assuming he is a coiner).  The attackers troops are safe in cata until the attacker chooses to send them.  After the attack, the troops are automatically recalled and tucked safely in cata.  The attacker chooses whose stuff to attack, chooses whether to spy first or not.  If the attacker makes a poor choice and takes a big loss, it was still their CHOICE.  I'm not saying defenders have no choice and no control.  Defenders can see patterns and find the best times to harvest, who we can trap for points, etc.  It is simply that we have less control and less choice than attackers do, making for a much bigger risk.

Mehnslayer said:

I got collect 6k gold for 2 necros, too sit on a hamlet for 3 hours would require the loss of more then 2k offense

Most of the blind attackers I've seen hit with more than 3 million offense.  It may be different depending on your area and level bracket.  Where I am, its easy to go an hour outside of tournaments, but 2+ hour quests are unattainable unless you have a lot of def to stack the hamlet.  Seems when someone attacks and fails, they keep coming back for more, even when there is no tournament going on.  I have no clue why.  All I know is I've had the same unattainable hamlet quest up for 3 days now and would really like for it to refresh.  2+ hours trying to get 9k gold just isn't going to happen in my area without putting out some serious defense and that would set me up for some very serious losses just to win very small rewards.

not perfect but are free rewards.... avoid during tournaments is mandatory