Something to consider also is if the WHM is DPSing or not.

If I spam Holy I can easily deal ~900-1k damage AOE + Stuns. This will draw A LOT of aggro and even the best tank out there cant hold aggro on multiple mobs. (WP SR or Coil 4)

A good WHM should know their limit based on engage time. My limit is 2 Holy before I pull aggro, 5 Stone II or ~4 Cure II. Use Shrout of Saints when you're close to that limit.

Spamming Cure I instead of the occasional Cure I + Cure II + Regen combo will also draw more aggro.

I personally find it best to let tank get hit to 60-75% of his health before I drop my first cure 2 as opener. (by the time your cast goes off his HP will drop to ~30%).
Follow with a few cures and never let Regen dissapear.

Healing is highly dependent in content and anything prior to Titan does not really require smart healing since nothing can kill you anyway as a WHM.