Downloading the LotV Beta without having an invite takes no third-party software. If you haven't found out how yet, it's really simple. You just need a some kind of command prompt, which comes standard with Windows, Mac, and Linux. You launch the Battle.net App with some special lines and that's all there is to it. It starts downloading as soon as it's launched.
You could potentially do this without even using a command prompt, by just setting a Shortcut's Target parameters with these lines, but I never got that to work. It only worked if I used a command prompt.
This is the lines of code: -game=s2_beta -install
Two dashes (-) does a strikethrough, which makes that look weird here. But you need TWO in front of "game" and "install" like "- -install" (Without a space)
Also, I think the LotV model format is different from Heroes, because I just tried the Heroes to SC2 M3 converter and it didn't work.
EDIT: It does look like you already figured it out, but I'm just making sure.