I mentioned it on another "find an upgrade" suggestion thread so I'll just copy and paste most of it here:
Since wowhead.com initiated the built-in weighting system it might be easiest to use the pre-fabricated ones. Grab the current spec and have it querry wowhead using those pre-defined factors. So a holy/disc priest wowhead would give you this Weighted Result
Edit: The only times where this may become a problem is when wowhead has multiple prefabricated specs for different talents. I.E. feral druids get "Fearal Tank" and "Feral DPS" on wowhead. In this case I'd suggest using the spec that's more prevalent in the community.