No, hell no, and please stop trying to ruin the game to "fix" things.
This thread scares the livin s*** out of me. The last time I saw a thread like this is was 6 or 7 people talking about how wonderful it would be to nerf Improved critical and just solve all the games balance problems in one swack. I thought the thread was silly and that the Dev's wouldn't possibly give it credence, for surely the massive availability of eleventy billion attacks per second + a dozen affixes stacked up was the main issue with OP melee in the game (TWF, Wolf form, Fury shot, Shuricannons, and repeaters being what they are)... and so I moved on just like a lot of other people dismissing the thread. Big mistake... the Dev's don't know whats overpowering content so they went ahead and nerfed primarilly flavor builds, and S&B.
I have the same initial "they can't possibly take these 4 guys serious" reaction to this thread but it's obviously dangerous to ignore terrible ideas on the forums, so please stop trying to call the games strength "a problem". There's no problem here you are solving. Just arbitrary limits that make some players feel better because they don't want anyone else to have a better build than them.
To the OP, Multiclassing has been a integral part of D&D for about 3 times longer than DDO has existed for... Your perception of D&D being about pure classes couldn't be more wrong.