I hope you realize that this isn't very useful for playtesting. It will give you a general idea of how things work, and may clue you in on what to expect, but ultimately tells you nothing about what the actual versions of class abilities you have in your current documents do against Monster X in Situation Y.
You have to beat the actual, current rules against the walls hard, to see where the current system breaks down. Otherwise you're going to be doing the 4e version of the Polymorph Dance in a year and a half, with a mob of people claiming that class X sucks and class Y is broken. And being able to pick up such and such Wizard ability will allow a Warlock to win every fight at level Z.
Its a grueling process, but it needs to be done well to create a good product. And if the playtesting indicates that big sweeping changes need to be made, you've got to break down and make them.
And just playing the game like normal *isn't* playtesting. I've been down that road before personally. I'd suggest you ask Troika Games where that type of 'playtesting' leads, but they're out of business. And that came out rather harsh, but I actually meant it in a friendly, useful warning sort of way. Casual play just doesn't catch the problems that systematic playtesting does.