I don't think I'd classify any "build", if it's really deserving of that title, as not being viable. Literally, ANY combination of skills is absolutely viable for any character. As long as you have a primary damage skill you can advance through the gameworld. Even if you develope the damage skill later than sooner.
?Using the OP's, as an example... Even if you tried using a certain spell like Telekinesis, that's just a single spell in the school of Alteration. One doesn't start out with a spell like that and had to have used something else prior to getting it. That still leaves the rest of the skills open for attention. I don't consider Skyrim's skills to be diverse enough to say that one can create a character that they couldn't easily lead them into another direction.
However, I have discarded several characters on occasion, not because their build wasn't "viable", but due to me growing bored of the character. Again, one just needs a primary skill of dealing damage. The rest is sheer personal choice and doesn't really matter, in a sense. EDIT : Let me reflect on that a little better...
They matter in terms of defence. I mean one has to be able to defend as well. This of course can come in several different allocations. Be that Heavy Armor, Light Armor, Block, Stealth, a massive health pool or from the simple act of avoidance ( running away ). That really comes down to playstyle. The main thing you need is a means of killing.