Every great landing page testing program requires a team of people working in perfect harmony. You need someone with product knowledge to suggest which product features to test. You need someone design folks to bring ideas for UX, colors, imagery. Great copywriters contribute their ideas for both the wording and format of the text content of the page.
It's a tricky thing to orchestrate, and the best processes are created and honed over time. You want to get everyone's input, but you also have to avoid failing through the "design by committee" mentality that besets some teams.
If you're lucky, your team may end up working together like this band, Walk Off the Earth.