This one stings a little, considering Blightsteel is one of the biggest, baddest artifact creatures to exist. However, I hate 'I win' cards in cube (hence why Channel isn't in here), and Blightsteel is too difficult to interact with.
Triplicate Titan plays much nicer - it will still win quickly if left unchecked, can actually be reanimated, plays well with Sneak Attack / Welder-style decks, and so on. Blightsteel only really fits in a Tinker shell, which I'm concerned might be too strong anyway. If players need to cheat out a threat that's very hard to kill, Inkwell Leviathan is meant to fill that role.
While Blightsteel is going on the sidelines for now, if it turns out that the cheat-y archetypes are struggling, I'll happily toss him back in. Time will tell!