Adrenaline

Following a Champion guide that uses "first to strike, last to fall" ascendancy skill. I am having trouble understanding the Adrenaline part, seems like i need to take huge damage before i get Adrenaline?
Just seems like a useless skill?
Thanks.

There are many ways to get yourself to drop to low life condition.

You can reserve a portion of your life with a reservation skill and arrogance support. (Just long enough to get adrenaline, not permanent). Pick something that will reserve JUST over 50%, you dont want to turn it on and get one shot because you dropped to 100 life.

You can do this on weapon swap. Swap to other weapon, enable skill, then swap back. If you put the skill next to weapon swap, its easy. X, Z, X. However make sure your permanent auras are not on your weapons or they will turn off.

You can use petrified blood, then life flask over it, then drop back under, etc.

If you want to proc it reliably/consistently you could use petrified blood (a much less likely / clean alternative is LL or blood magic + flask setup). But it seems like a decent node, Adrenaline is a really powerful buff with a long duration and the ascendancy also instantly heals you for 25% and removes ailments when you drop below 50% life and gives you 10% more damage with intimidate (less than 10% if you have other sources of increased damage taken).