to tell the truth, all the beetles look a little like adust mite. I got bested by the first scorpian two times. so I kept training until I knew I was ready. I was ready when I got the Iron Spartha. I took it out in almost one hit! I like to do that. always train and make sure I'm prepared for an upcoming battle. because the last thing I want to do is die again!
I think this is a good Idea. you should put the Crypts on the 'High Ground' area, because the Crypts already have a long range, so the 50% bonus will give the Crypts the highest bonus.
this is what I did on one of the levels. I raised my mana bar to a 1000 so I could build a trap, and I kept recruting Hobits. not strong, does not have a high health amount, but in mass numbers, they took down about 10 trolls, and about 20, YES, 20 OGRES! YEAH! die bad guys!
 "Castaway"){kind=icon}
 "Cursed Treasure: Don't Touch My Gems!"){kind=icon}
 "Dragon Boy"){kind=icon}
 "Epic war"){kind=icon}