Where do people check accurate WoW DPS rankings?

Warcraft Logs. It's the only one built from what real players actually did in real raids rather than a sim of a perfect rotation. Look at the spec rankings for the current raid and filter by the percentile that matches you, the 95th percentile numbers are not what you'll pull. Sims like Raidbots are great for your own character but a terrible way to compare specs. Also any tier list that doesn't show which boss it's for is guessing.