If you are using Twist of Fate, for whatever reason (its actually VERY good with fights that have tons of adds because you end up with 70% or more uptime on it), you should use this trick.
- Remove all gear.
- Notice low HP.
- Equip all gear right before the pull.
- Heal yourself (you'll trigger Twist of Fate because putting your gear back on gives you more HP, but you're not auto-healed to full).
- Use your Potion, fight starts, win.