I understand your frustration about gaming Visible but I think most of the abusers are only violating the spirit, not the letter of the Visible swap deal. If you read the thread on the E6, a lot of discussion was about what kind of phone would Visible accept. What Visible advertised was that you had to send in a working android phone with an IMEI. It became apparent later however, (via chats with Visible customer service reps) that you could send in phones with a broken screen or some other defect, as long as you could power the phone up and use it. Then, people found out that you could send in old android phones with MEIDs but not IMEIs. Then people starting pushing the envelope further by sending in totally defective phones without batteries, claiming that the battery was swollen and not safe to send via mail. Then people starting swapping old iPhones and feature phones. In sum, the universe of eligible swap phones has expanded greatly, to not necessarily include just working Android phones.
The reason why people are using virtual CC numbers for payment is not because they aren't not sending in swaps. They are, but people are sending in arguably ineligible phones and are wary of Visible rejecting them. The thinking seems to be that a swap rejection will be meaningless if Visible can't charge an account any further.
A secondary concern is that people don't want to take a chance on Visible charging for a second month of service. The latter concern is especially prevalent among people who have had bad experiences with other carriers, particularly MetroPCS.
Personally I've done 3 swaps, only one of which fit the exact advertised criteria that Visible set out. One was a Cricket android with IMEI but cracked screen and no battery cover; second one was a good condition Verizon android with MEID, not IMEI; 3rd was a fair condition ATT blackberry imitation Windows phone. I actually have about 6 more old phones that are plausibly eligible for swap, and anther 10 iPhone parts phones that are all icloud locked and/or water damaged, which I would expect to be rejected. However, I'm sure there are lots of people in my position who would have already swapped all those phones to get new phones to re-sell on eBay, especially taking care to use virtual CC #s for the iCloud locked phones. But for me, it would not just be abusive but also wasteful, because I would not be taking advantage of the month of service that I'd still be paying for. So I'm just going to drag things out with the 6 plausibly eligible phones and get a swap every month or two, for as long as Visible allows swaps, and also take actual advantage of the service.
The iPhone SE deal is also just a plain good deal, even without a swap. But virtual CC numbers are certainly not being abused with that deal because the $200 gift card only comes after you've completed two months of service. I predict that Visible is going to either stop that deal or have the SE's locked for 60 days just like Verizon postpaid does now.
The main thing you should keep in mind with any Visible deal is that you have 60 days from the date of your order to activate your SIM. So if you expect that you will need new service within 60 days and you see a new deal come up like the A10, you need to jump on it as soon as it comes back.