Is this life flask worth using

Yes but mainly no. Since you're new probably not. The recovery is very low and it's just used in a couple of builds that either don't use life flasks as recovery like CI(Chaos inoculation) builds. Or some builds that don't rely on life flasks for recovery like a thorns build. 

If you have a build where you don’t need a life flask people use this because of the line that says no inherent loss of rage.

There's a passive node in the tree that gives you rage per use of your flask.

That and this flask combined and you can stack rage on a bow/crowbow build - and keep the rage stacked up. Hugely increasing your DPS.

You also get rage every time you're hit

But obviously you don't have a flask that recovers any health as a trade off.

But the flask is pretty common and there aren't many users - so it's not very valuable

Situational depending on your Rage stacking requirements and how survivable you are without a reasonably sized heal from your flask

Great flask to pop before you go on a cocaine bear rampage.

It's pretty much best in slot for CI rage builds that don't have inherent rage regeneration.

Good for Recoup Chrono

Was bis for my blood mage last league as defiance user.

It's a life flask for builds that dont need a life flask.

No.