Timing the load of a single dom element [on hold]

I need to find a way to time how long a single, particular DOM element takes to load, and I'm not having any success finding a solution on the internet.

On a the web site, I can see that there is a particular h2 that is loading much later than it should. In order to test this issue's replicability, and to determine whether any of my team's solutions are having a positive affect, I need to be able to record the actual amount of time before the element loads visually loads.

I have already looked into casperjs, but it's waitForSelector() function takes over a minute to trigger, and this goes contrary to what I have seen while visually testing the site.

Does anyone know of any technologies or strategies that could help me solve this problem?