I think everyone experiences The Cube in the same way at first (at least at lower levels). It's hard to figure out what it's really good for... especially with a 6 mana.
I bet the more you play it (and perhaps level it up) you'll find it pretty useful.
Initially I thought it'd be best as a tank in place of Lord A, a 'poor man's Lord A', if you will... but really, I think putting it further back and protected (with heal) it can really destroy (by outlasting) a team.
Thanks for sharing!