you wanna use these addons:-
gladius:it shows your arena opponents , when their on cc and how long their on cc, it's great for layer cc, for example your warrior happenss to be lucky enough to be within range of both your opponents , he could burst out a fear you will see it in gladius, follow it up as soon as the count down is down with a hex and that will usually have the healer blow a trinket or bubble.
Loose control
ersonal favoritee especially in these days of stuns and cc, you wanna know immediately what cc your under and how long
totem timers: shows your totems ins a samll visible frame and their duration , important to watch especially when you have opponents that hate totems , has saved me alot of trouble as resto since people love killing my mana stream totem and tremor totem.
as for unit frames addons you want one that is flexible enough to allow you to move and customize the size for your focus frame, i would suggest xperl, but almost every unit frame allows such flexibilty.
cast bar mod for focus target: i use quartz , though i did use ecb in the past which wasn't bad, it's very customizable so you can better adjust the size of your focus bar and even your cast bar if you want.