Why would you need HF with 100% uptime? You can use it only when your tank is getting heavy damage.
It’s true that you don’t need fumigate and beak mask, but level 1 is good to use while bloodletting is down.
I’m not sure about Pandemic though, but if you are getting it, it’s a good idea to max it, sine it will spread single target debuffs from other characters to every mob nearby. Yet I don’t know what can’t be spread through Pandemic, that’s why I won’t advice it over other skills.
Generally maxing incinerate is good idea, damage per level is decent and it’s AoE.