InfernoReversal, I appreciate you taking the time to review my champion concept.
In all honesty, Dalek is not intended to be an assassin character (and I edited his tags to mirror this). He can poke and provide some minor support from behind the team, but his true purpose is to deal massive amounts of damage whenever the fight actually begins and you get into unavoidable melee.
Fizz is made to poke and run away, and he makes a good assassin by doing so. Dalek is made to deal damage inversely proportional to the distance between him and his target, and will be a unique mage by doing so. The detonations will give you a rotation of moves to use on your way to the target, making Dalek very versatile. Unlike LeBlanc, however, his late game usefulness will not be degraded into becoming a CC machine - the proper order of detonations, followed by an execute from his E, will allow him to keep up his damage output though the game.
I'm sure another melee assassin or off tank would be nice in the league, but Dalek is a Mage. He does bursts of damage, and his "melee" role makes his bursts much more dangerous as he gets closer to his target.
In respect to your points, however, I have taken his "assassin" tag away and changed his E to being a targeted ability instead of a skill shot. I'll probably make one or two minor changes in addition to this, but I'll bump when and if I do so.