I couldn't find where this was mentioned

This is bad... anyone who attacks inactives higher than them will lose lots of exp
and I lose to so many people 5, even 10+ levels below me because of blocks/misses/guild helpers,

 it negates so much growth...

this really changes the game for me....
icky

Really? I thought it made more sense like this.
What if the lost exp was much less than what happens when you win?

EDIT:
Should attacking be a risk free environment?

I get losing money, but I've never played a game where you lose exp from losing an attack(edit: in fact, I've played a couple where you still gain exp); I'm in negative for the people at or below my level already...

the block stat is good enough...

Well you do lose credits... (depending on how many attack turns you use)

Whether you win or lose your experience should be affected. If I was to attack KPT I would expect to lose exp and not just cash.

I feel like this is the right way for it to work.

I don't know, it can be turned on and off at ease, but I don't really see any problem yet.