"Moar DoTs! ZOMG, stop the DoTs!"

What does “clipping” mean?

When a spell is ticking, whether it’s a HoT or DoT, it’s going to have a final tick on that last moment before it expires. If you fresh it, you’re denying your spell that last tick and starting it’s ticking all over, which means you’re essentially “clipping” off that last tick.

Give me an example.

Let’s say you have a spellpower of 2500. You cast Renew. Given Renew’s 188% spellpower modifier, divided over 5 ticks, your spell will look like this untalented:

(1400+2500[1.88]) / 5

This gives you 6100 healing over 5 ticks of 1220. Your Renew heals every 3 seconds, so you will tick 1220 on your target at 3, 6, 9, 12, and 15 seconds.

But you panic and decide to refresh Renew early; you cast it when it’s only ticked 14 out of its 15 second duration. Now your tank is being healed as follows: 3, 6, 9, 12, 17, 20, 23, 26, 29.

Wait, how’d I get that?

If you Renew at 14 seconds instead of the full 15 second duration, you “clip” your 15-second tick. 17 is the number the next tick will occur at from the second Renew; 14 + 3 seconds = 17. You can imagine how frustrating this could be for a healing class that’s HoTing up a storm, like a tree!

Why is clipping bad?

There’s two reasons to avoid clipping your HoTs and DoTs:

1. You lose the last tick, thereby less HPS or DPS.
2. You go through mana faster. If you wait the full duration, not only is your HPS/DPS going to increase, you’re going to refresh the spell less often.

How do I avoid clipping?

It’s better to let a DoT / HoT expire while spending an extra second casting a different spell than to refresh it early.

Let’s go back to the example above. The “clipped” Renew resulted in 3, 6, 9, 12, 17, 20, 23, 26, 29. Had the priest used Flash Heal (or any other spell) to occupy that one second of tick left, then even though Renew would’ve been delayed by 1.5 seconds (assuming no haste, the 1 second GCD, and Flash Heal’s 1.5 second cast), it still would’ve ticked better: 3, 6, 9, 12, 15, 19.5, 22.5, 25.5, 28.5, 31.5.

Half a second faster, one extra tick, and an extra Flash Heal slipped in. The win-win situation is clear.

This applies just as much while smiting and trying to figure out whether to cast that extra Smite while Shadow Word: Pain expires or refresh SW:P early. The Smite should always be the decision.

Clipping channeled spells.

Channeled spells like Penance, Divine Hymn, and Hymn of Hope can also be “clipped” if another spell is cast before the channel is complete. Since all of these have cooldowns, they’d only be clipped if you cast another spell; but on the DPS side, a prime example of channeled clipping is when Mind Sear or Mind Flay is cast again before the full channel expires. Make sure if you’re going to cast the same spell back-to-back that you give the first spell its due course.

How did you come across “HoT Clipping”?

Trienish the Shadow Priest was teaching me how to Shadow the other day so that I could become more familiarized in all three of my trees. During our raiding lessons, he brought up the idea of “DoT clipping” and how I should always let a DoT tick its full duration. Since I think like a healer all the time in WoW, pewing or not, the first thing that came to my mind was, “This must apply to Renew too!”

Monkey wrenches involved in clipping.

Haste rating will always affect your cast times and GCD, so make sure you’re aware of what your toon’s capable of when figuring out when to refresh your DoT/HoT–just don’t ever do it early! Also, there are mechanics that will throw the idea of clipping off, like Empowered Renew’s “insta-tick” effect. Make sure to use your judgment.

Interested in how clipping affects non-mana classes? Read on Feral druids and DoT clipping.

Thanks to Lucky7s76 for the share-friendly image on Deviant Art.