How do you watch for boss mechanics while healing?

[Lyrica_Ashtine]

I don't know if you're using FT, but if not it should be quite helpful so you can always see what the boss is doing. I've definitely noticed that certain mechanics can be easier to deal with through the game's customizations.

I'll just point out that this isn't always the case. Not every action that does significant amount of damage or requires attention has a cast bar or indicates where the damage is going. Some examples:
Any cleave-like attack without a cast bar
A particular dragon type you can find in Stone Vigil hard, The Aery, Nidhogg EX and other areas
Tailscrew in Satasha Hard
When the gorilla gets agitated in Hullbreaker Isle

So, again, I suggest you to keep your eyes on the field and not glued to the text. Glance at it frequently, but don't tunnel on it.