Based on my observation, Tobi just used Kamui for the first time today since the beginning of his appearance.
For story purposes, if Kishi made Tobi use Kamui early on, then half the suspense of finding out who he is would have been taken away. So my assumption is Kishi will explain to us that Tobi, through his power and Senju DNA, was able to use the S/T jutsu without MS. He probably knew the the affects of MS but knew how precious that technique was, so he made it his business to find away to use it without going blind and ultimately losing it.
If any of you are familiar with DBZ, its similar to when Goku/Gohan trained in the hyperbolic time chamber to the point where they can naturally sustain being a super saiyan without using up their Ki.
Kishi made it obvious to us that this is THE first appearance of Tobi's Kamui MS form when Tobi said " Having a borrowed power that you can not fully use is not enough to intimidate me, HERE'S A TASTE OF THE FULL POWER OF KAMUI!!"
This means the level that Kakashi is using kamui with MS is not the FULL POWER OF KAMUI! What Tobi can do with his normal sharingan, Kakashi has to use MS for, is how I interpret the statement.
You want an Eye problem, well here's an eye problem....when is he going to use his RINNEGAN?!!! I know kishi wanted to build on "Obito's eye' but he has an even more powerful eye sitting in his left socket unused. thats quite unreal to me.