I think it's a pretty powerful class as it is. Keep in mind that Still Spell is better than Armored Mage, though. You also can use it in grapples, and combined with silent spell, unless you have to use an expensive material component, nobody can identify what spells are being cast. Especially since the ones with visible effects are... well, invisible.

If nothing else, you need to split those abilities up and move them further back. Perhaps at 1st level you get Eschew Materials, at 4th you get Invisible Spell, at 8th you get Still Spell, and at 12th you get Silent Spell or somesuch.

It's just too front-loaded right now.