Chakra or Shield Mastery?

Nah, Chakra lvl21 heals 1000~2500, Chakra lvl30 heals 2000~3500 at level 120 (Healrate depends on total luk+dex and Skill Level). There's a lot of difference between lvl 21 and 30... Especially when you're using it to survive.

Most people who say Chakra sux have lvl21, and die while using it... and get angry...

P.S. I was just luring them, I wouldn't have saved any time while fighting three 250.000.000HP bosses myself with using pots instead of chakra.

I don't use fucking Chakra to survive o_o