While I agree that there are too many "warlo-" classes, I think warlord should be the one to change. To mean, being a warlord implies leading huge armies to invade foreign lands. Not something your average 1st (or 2nd, or 3rd, or...) level character will be doing.
Warlock, however, I like. I think, for most people, it has a relatively open flavor. I mean, it's fairly generally accepted that it's a male magic-user of some type, but beyond that, most people don't have too many preconceptions about what it should be.
The word "witch," on the other hand, makes me think of goofy halloween costumes and lawn decorations. I think the image of the witch as an ugly woman with green skin and warts, riding a broom with a cat, is too fresh in most people's minds to see a "witch" as anything other than that.