I agree, Kessen is powerful.
But, can we not BOTH use Kessen? He is just as powerful to Imps as to Rebs, it is a dual faction item, exactly the same, same power, same features, same everything.
The reason, I think you may find, that he is so powerful, is that, as a tactical strategy, people pair him up with high level luggas (2 or maybe even 3) to give him a massive boost. Then, with good fortune, they could potentially line kessen up to hit your SC. I myself have been hit a few times by Imps using Kessen, and I say fair play to them. If it works, it works.
Quick question - are your deka/deko in close proximity to your SC? If so, it is actually those that Kessen is targeting, and hitting your SC is a direct consequence of them being either in front or behind them. Perhaps check over your base before going to defense, to make sure that it wont be easily lined up this way.
I would say a level of unfairness is how Imps can use eATAT and crabs to destroy a base, even lower level attackers, without really needing much of a tactic, and when they trip SC, simply send the level 10 bikes in to destroy what comes out. Where is the thought in that? What a basic strategy, a child could do it. Doesn't that essentially render the SC useless anyway?
I'd say, if you are so in awe of Kessen as you seem to be, get him, use him. End of.