In MLA fields, acceptance rates at journals can vary widely. Many of the "top" ones accept far fewer than 20% of essays submitted, so if you're batting .500 at the outset, then you're doing surprisingly great! Have you checked the MLA Directory of Periodicals, in which most journals list their acceptance rates? (It's voluntary, I think, so the numbers may occasionally be fudged, but at least it gives you an idea of relative selectivity.)
Revise-and-resubmit is indeed an invitation to do so -- once, with an essay of mine, I took that response as a negative, but then four months later the editor emailed me to ask if I'd done the revisions, for he was interested in publishing it. Also, while a straight-out acceptance with no revisions feels great at first (hooray!), the other forumites are right: you'd prefer the critical feedback of your peers and the chance to improve your essay pre-publication.
Also, a rejection is not the end of things, of course. More common, I think, is that many scholars "aim high," i.e. for an extremely selective and well regarded journal, then if rejected outright, submit (perhaps after revising again, and definitely if the rejection came with feedback) to a somewhat less selective journal. Unless the essay is really unworthy, it will probably find its way into print somewhere. (And if it is really unworthy, you don't want it in print with your name on it.)
In conclusion, your whole percentage-poll is really wrong-headed, I'm afraid. I could say that 100% of my submissions have been accepted (eventually), while a number were either rejected (but later accepted elsewhere), or R-and-R'ed (so, eventually accepted at the original destination).
By the way, even rejection is not so bad, as it gives you feedback to help you improve the piece, thereby increasing the chances both it and others like it get published in the future. Congratulations on the already accepted stuff, and best wishes on the future work!