Firstly, this may sound critical, but realize from a player's standpoint your game ad says all we may know about you as a DM. Phrases such as "Novices need not apply. Sorry, I just don't have the time right now to go through all the hoops." Say to a person: while you want to run the module you will be unwilling to help a fellow player grow in their knowledge base of the gaming system and therefore grow as a contributor not just to your game, but the Weave as a whole. I've been playing D&D for over 10 years and when I started playing 4e here...Needless to say my DM's have been VERY patient and nurturing. Not only did that make the game run smoother, but further down the road, should I get into another game, I will have a much more vast knowledge of the system, I may even help other players. (insert ripples in the water metaphor) Furthermore, this post may help you become an even better DM than you are now. I could have said "I only post in the ads of Veteran DM's" But where would that get anyone? The first and foremost thing is to be INVITING. I would suggest you look at some of the more successful ads, where you see a lot of people applying. Check out the recently closed "Courts of the Shadow Fey" in the 4e section. There were DOZENZ of amazing applications. Sure some of them were applying just because of some aspect they liked, but overall it is you, the DM who set the tempo for how many people apply to your game. You alone possess the power to inspire people to come up with brilliant/crazy/interesting/useless characters to help you build your world.
Furthermore, being one of probably thousands of people on the Weave (let alone the net), you would think it may not mean much if a few people decide they don't like the way you have posted an ad and don't apply. But I would disagree. If I meet a rude person here (I don't think I have yet) I would be much less likely to ever apply to a game they made, or possibly even one they play in.
Lastly, information is key! When you create your ad, you already have a lot planned out (you're the DM after all). But as a player, I know only what you tell me. After you finish your first draft (yes, I said first draft) of your ad, take a moment and read it again. Don't look at it from your perspective, look at it from mine. What questions would people ask after reading it? (No, I won't list them all). The way I see it, the less questions on mechanics people have after reading your ad, the more successful it could be considered. There is so much more I would write, but in my opinion these are the biggest two reasons you might be seeing a low application count.
No one is perfect, but I'm more than willing to forgive you if you forgive me for that spelling error in the first paragraph. But hey, that's just my two cents...