I think it's really too strong compared to all the other summoners.
Each summoner provides one attack point, Yodin Zaku also provides Blast ability to all monsters. This is like a boost of 2 or 3 attack points at least. Not only that, imagine how powerful monsters with Snipe will be, or how strong this summoner will be in some scenarios such as "Target practice" or "Back to basics". Maybe I'm wrong, but this summoner seems really too strong!