OmniBar dynamically shows cooldowns of your opponents or enemy's in pvp with an easy to use interface. This addon was born in MoP and has been backported by Lanrutcon on his Github. However, there is a known bug:

Issue was in the conditional for sorting by time remaining.  If they didn't fall into the first condition the second condition had an inline comment which isn't supported in function arguments and would throw a Lua error and would also cause that icon to no longer show up -- Theroxis (Apollo Discord)

His "fixed" version is available below, re-uploaded by me from the discord. This should be the version you download unless you are worried about security and would rather grab the original backport from Github.

NOT TESTED BY ME!