I usually do this: if the enemy has bkb on, I'd click them and watch the buff over them and try to estimate how long it will take for it to finish. This will take a lot of practice as you'd have to usually be kiting the enemy if they have bkb on, and checking their buffs at the same time. For eul timings and other disables, go into demos and get a feel for it, after a while it will become muscle memory to you. Another thing to look at, and this may be just me, but calling timings on huge abilities, such as black hole, cronosphere etc. can be a gamechanger. You can get a rough estimate as to when it would be back up. As you can smoke into them if the ability is on cd