Arctic Armor - how is it not useful? Enemy hits you twice = enemy frozen. That's a great talent.
Fashion Plate - it's useful for anyone who wants to wear heavy armor without investing heavily in Strength. That seems pretty straightforward to me.
Head Start - you seem to think that you must choose Head Start INSTEAD of investing in Attribute points. You don't. You can do both. And yes, everything else you said can be summarized as "you get a bonus early in the fight, which becomes a penalty the longer the fight lasts".
People won't make all of their characters Witches to get that talent. If they did, then they've already sacrificed a huge amount of ability points forming a redundant party.
Tenebrium - the problem isn't whether you can powergame it or not. The problem is that its stupid. It makes all of the weapon skills meaningless halfway through act 2, and reduces the variation in character builds. That's two different flavors of bad design.
