C is for cookie, that's.... about as much of that song as I want to put in anyone's head.
For now...
Del is my go-to for highest summoner in my deck. He's cheap (ya, costs a few more power to use..) and he's been easier than most to level up. I think the reason the defender is so low under the radar is that he is not all that easy to collect, compared to other cards and rewards. My better half has one that she LOVES to use. She's been building it for a while, and it has helped her hit Champ 3 a few times now.