They probably don’t have a max level, like in Siralim 1. They can go as high as you want, but start to cost quite a lot.
That’s not a bug. Those perks have no level cap. Unless you cause an integer overflow (HIGHLY unlikely to happen!), you can level that puppy 'til the cows come home.
So yes, you can get all of your creatures doing a hard 300% bonus damage with each attack. Though I haven’t played either game particularly far, I get the feeling you will need it after some time.