If you were going to run D&D in a world without magic (or at least one where magic is rare and subtle), in a setting something like medieval Western Europe, what classes would you include? Would you just do classes with the martial power source and that's it, or do you think there are ways to sneak the other classes in?
Simply using the Martial classes would be fine. Your players would be short the controller role. Using all the options from MP 1 & 2, the martial classes can pick up some of the controller slack through AEs, grabby Brawlers and the like. The Essentials Hunter Ranger is a controller, but you'd have to strip out it's more overtly magical Primal powers, like Stalkers Mist (one of the few things that sub-class really has going for it).
Two other sub-classes you might consider allowing would be the Skald and Berserker, just strip out their non-martial powers (Which means Berserkers only freak out when bloodied, and you'd have to rule that the at-wills don't gain the Primal keyword).
And, of course, you'd want to switch on 'inherent' bonuses, and retain 'Masterwork' Armor, to keep 'the math' on track.
If you want more 'subtle' magic, you could keep the Arcana and Religion skills and a select list of rituals (less overt ones - no linked portal or anything) and ritual components (possibly more detailed and weird/hard-to-find than expensive) that fit the tone of magic you're going for. Retaining some Alchemy might also be an option. Would-be 'wizards' could use a combination of Arcane knowledge, legerdemain/sleight of hand (Thievery), and rituals - Rogue, possibly with some sort of custom 'Charlatan' theme or background, would probably be the class to use for such a 'Wizard.'
And... what about monsters?
You could restrict yourself to humans and animals. Or you could include less overtly magical monsters, like Orcs, dire wolves, and whatever. Limit yourself to Natural creatures and avoid undead, magical beasts, and constructs.
Another thing you could do is make the natural world distinctly non-magical, but still make it possible to delve into the more-magical Feywild. Fey - and mortals trained in magic - could use magic in the Feywild (swapping out martial powers for arcane or primal), but not in the natural world (where Fey would presumably also get to swap out their un-usable magical powers for martial ones).