I try to use as much of the default UI as possible.
Mainly because with a significant patch, a lot of addons will break.
And the default UI doesn't need an update.

I'm using Shadowed Unit Frames, as I cannot stand the default unit frame.
The information is much easier to read.

I'm using Grid for party/raid health and debuffs.

For the longest time I was using Dot Timer for buffs and cooldowns.
But that broke, and there wasn't an update fast enough for me.
So I have the default Blizzard buffs at the moment.

I'm using the default Blizzard bars.
Not all of them are visible, but 72 action bar buttons for Warcraft residing macros is plenty of space for me.
There are a few macros which reside within IS Boxer.
But 90% of my set up, is keybinds sent from IS Boxer to WoW, with warcraft macros on those keybinds.

I also use Deadly Boss Mods.
But mainly for pvp timers these days, haven't raided this expansion.

I've got a Damage Meter, but that's hidden usually.