Another note is a TB will one-shot anyone other than a tank, and I believe some can even one-shot tanks if they are not mitigated either through CD, sharing damage with another party member, or both. So be sure to sustain that agro on bosses, which is good practice in general, but can make a difference between a wipe and a clear in more punishing content.

Generally, you won't see too many TBs in casual content, and even the hard hitting attacks some casual bosses have are reduced to next to nothing when over-geared. Since you're leveling, and won't be over-geared like someone who is synced, these attacks will hit you harder but nothing a healer worth their salt can't handle. However, that is no reason for you not to get into the habit of popping a CD whenever you know your HP is about to drop. That just comes with experience as you learn the fights you repeat.