when i had my other acount a year ago, the host in my aliance decided he wanted to see if we can all take down a lvl 10 with all transports nothing else...AND IT WORKED!!! it took about 6000k all together when we all pichd in and did it. but i would never recomend trying this lol. we wer all being retarted at the time but it was awsome:P
it all depends on your hero attack, and what uv got in your academy to attack a 10. idk if u can do it now, but i used to farm a 10 with 60k arch and a bunch of trans to bring back the load in 2 waves. i was able to do this because evrything in my acadmy was all the way to 10 and my heros attack was abnormaly higher then anyone elses.
so..it all depends upon what youv got. experiment with it for awhile till u get it down