Just took one down for the first time, alot easier than I thought it would be.
Had all lvl10 researches except HB riding which I am researching now.

I hit it 36 times and I think an alliance member hit it 4 times during the fight.
Lasted 32 minutes and am still calculating losses.

Used 8 heroes, gained 41 lvls and 9 medals I think, no bonus items.

Used corslet horn and a penicillin I had laying around.