I agree with Suzeeq. The concept behind what you are doing in moving the 2 stitches is based upon altering the tension point between the needles and it's one that I've used successfully; however, if you consistently do those same 2 stitches, all you are doing is changing the tension point, but there's still a consistent tension point, thus, the possibility for ladders.
There are 2 things I do for this in magic loop, one is the the concept you are using, only very periodically, as in maybe once a pattern repeat (somewhere between every 4 and 10 rounds or so, give or take, a fine gauge yarn, you can get away with more, heavier yarns, make the number of rounds smaller) but like Suzeeq said, don't slip them first. When you get to the end of needle one, instead of slipping, just knit 2 or 3 stitches with the now free needle and then slide them down the cable so those 3 stitches are now at the end of needle 1 and then continue as normal. Just don't do it every round, you want to just "throw off" the tension point periodically.
The other thing I do, which has become just habit for me no matter what kind of in the round knitting I'm doing, is tugging at the 2nd stitch of each needle. So you knit 1 normally, insert the needle into the next stitch, but before wrapping/picking, give the working yarn a good pull. This has pretty much eliminated the need for changing the stitches around for me, except in straight stockinette with unforgiving yarn maybe.