Here's a good piece of advice for managing your bars and making it less complicated.

There are a LOT of abilities. But there's also a handful you won't use as well as a good chunk of them that you only use on demand.

A good way to manage all of this is macros. You can macro some of your defensive/offensive abilities into one button.

You can macro things like mercy stroke (finisher ability) onto one of your regular abilities (since it is only used at -20%.

You can also activate the l2+r2 ability bars as others have said.

What I have done with them is change both l2+r2 and r2+l2 to display the same bar so that there's never any confusion.

Some may argue that this is inefficient but it greatly reduces the amount of micromanaging you have to do and I have cleared all raid content with this setup.